This will probably be my last post about bluejacking, this site is starting to look a bit over-focused on the topic.

Over the last week, my girlfriend (who works at a large local school - 2,000 or so pupils) has been wandering around the school with a Bluetooth phone set to discoverable, and named after her. I couldn't think of a more tempting target for a bluejacker than a member of staff. She didn't receive a single message in this time.

However, on the train home from London one evening I was bluejacked; my Powerbook is called Susan (don't ask) and "Bertie" asked me how I was. "Bertie" then stopped receiving responses. We were in transit at the time, but I looked around and couldn't see anyone who looked younger than twentysomething.

My conclusion from this entirely unscientific and anecdotal study? Bluejacking is the province of students and young professionals, not teenagers. It's not a widespread activity by any means: captive audiences on trains provide a distraction for bluejackers. It's not a means of communication, as such: I have yet to hear of a 2-way conversation been carried out over the medium. As such it poses little threat to SMS revenues.

Here's an unformed thought: mobile billing has always been about aggregating small charges: a text message here, a voice call there. Implicit in this is the idea that tiny changes in consumer behaviour, expressed over a large population, can make a big difference to those profiting from these changes.

For example, imagine you're a hypothetical UK operator with 15 million customers, and you get them, on average, sending a single 30 pence MMS message each month. That level of traffic is pretty minimal, and I'm sure wouldn't help analysts perceive MMS as having been "successful" (as if there is any such binary test for success with these things!). But it would bring in £3.60 p.a. per customer, which translates to £54m annually purely in message charges.

I also suspect there would be knock-on effects - that receiving an MMS typically stimulates a response as a text message, or as a call. Or that owning an MMS-capable phone makes you more likely to use other chargeable services, like gaming or an online portal.

Even without these extras, it's significant extra revenue from a small change in behaviour. I'm not suggesting that bringing about such changes is easy, of course. But many new services seem to target a small subset of overall mobile users, and ask them to pay significant sums - a pound per month, 5 pounds per month. As operators demonstrate every day, this isn't the only approach that works.

I can't believe this is an original idea - if anyone has seen a reference for it elsewhere, please pipe up.

The problem with SMS spam is not so much receiving it as its interruptive nature: you think you have a message from a friend, stop what you're doing, open it, and it's some crappy promotion you don't care about. We're (unfortunately) quite used to being pushed information that doesn't interest us, it's this masquerading as a contact that we care about which really grates.

How about this as a suggestion: have a setting on your phone which says "only alert me to messages from people in my address book". If a message from anyone else turns up it's dealt with as per normal (appearing on your phone screen and in your inbox), but your handset doesn't vibrate, beep, or otherwise get your attention.

This wouldn't get rid of the problem, but it'd be a practical step towards reducing its annoyance.

I've had a camera-phone (or phone-camera, depending on your religion) for about a year now. It's long since passed having novelty value for me, and I find myself using it regularly even now. I even send MMS messages occasionally: mainly to my girlfriend, though occasionally to one or two other people who I'm fairly sure can receive them OK. A couple of weeks ago I was chuffed and amazed to receive an MMS from Disneyland, Florida; I still can't work out quite how it got here.

When Dom and Eva came over a week or so back, they brought digital cameras with them - and being quite into their photography, did an awful lot of snapping away. The result: some really high-quality photos of our cats, one of which now graces my desktop.

And there I sat, quietly bemoaning the shoddy quality of my 640x480 pixel Nokia toy, which seems to blur half the pictures it takes, has no flash, no zoom, and produces nothing remotely professional in output. I was thinking about this over the weekend, wondering when decent quality cameras would turn up on phones, when it struck me: it doesn't matter.

I'm not saying that cameras in phones won't become higher in quality or more full-featured: as this stuff gets cheaper to manufacture, they might as well get better - the difference in cost between a poor camera and an average one will become negligible.

But think about the audience for photos taken on cameraphones; right now, they're still used a lot by tech-savvy folks like myself, people who write online journals, and so on: folks who want to look at their photos on a PC or laptop. This is changing (more and more people I know are getting them), but there's still a tendency towards the gadget-lover amongst cameraphone owners, I'd say.

Long-term, this won't be the case. Long-term, pictures taken on cameraphones will be viewed, principally, on other phones. And this is my conclusion: the important thing is that images produced by phones look good on other phones, not that they produce high quality media.

It's just like text messaging: just as a phone keypad makes text entry difficult but possible, and the results are poor grammatically but worth sending nonetheless, so an embedded camera which takes poor quality photos is still worthwhile and acceptable if these photos are only being viewed on a tiny screen.

Apologies if this is obvious. I'd never considered it before.

If you spend your time, like I do, reading up on developments in the magical world of mobile, then you've probably come across the term "bluejacking": it's the practice of using your Bluetooth-enabled phone to send a message to another handset, and works by embedding your message into an entry from your address book. Remember how it's easy to beam entries from your address-book to your friends using infrared on Nokia phones? It's a very similar thing, but more often used to send messages to random strangers who happen to be near you.

Bluejacking is getting a lot of press. It's sometimes described as a craze, we're given the impression that it's on the point of becoming widespread, and the name itself makes the practice sound more like a dangerous subversion of other peoples phones than the vaguely annoying and rude prank that it is.

This has the whiff of hype to me, but worryingly, a number of people who I like and respect seem to believe that it is something special. So I've been wanting to post my thinking on bluejacking for a few weeks now. Here goes...

Why does this matter? Why is it useful to be able to send short messages to people you don't know, who happen to be within 10 metres or so (Bluetooth's range) of you? I can understand the novelty value of playing a prank on someone, but once that wears off, what does bluejacking actually offer? Comparisons with SMS don't hold up, for me: SMS lets you quickly and cheaply interrupt someone and get a message to them whilst bypassing social conventions and small-talk, and it's something you use in a very informal fashion to communicate (principally) with people you already know well.

This is not to deny that there will be interesting applications built around Bluetooth; in fact some are emerging already. But bluejacking won't be one of them.

Who can bluejack, and who can be bluejacked? What's the potential audience for this practice? Bluetooth-enabled phones are typically those marketed at business users: hardly a good fit with the teen demographic you'd expect to be driving this new "craze". And in order to be bluejacked, your handset needs to have Bluetooth activated and be marked as "discoverable", so that you can be seen by other devices in the locality. Many phones don't, by default, meet either of these requirements. So the audience is small.

Who's doing it? I've been trying to get an idea for how prevalent this practice is, and I'm going to conduct a few experiments this week to see if I can find out (which will involve leaving temptingly discoverable handsets lying around in prime bluejacking locations and seeing if anyone finds them). The only research I've seen is by a PR company with a vested interest in promoting bluejacking, and it beggars belief that 85% of the population know about this stuff. And the conclusion that "68 per cent would welcome the opportunity to receive targeted promotional messages or electronic coupons, but only on an opt-in basis" is completely unrelated to bluejacking (which is all about messaging people who neither know you nor have your permission to contact you in a rather underhand way).

So, who's bluejacking? As far as I can see, it's a few folks on the BluejackQ and Esato message-boards, plus industry folks with an interest in whizzy new stuff giving it a whirl (and there does seem to be an overlap between these two categories). This isn't a widespread practice, beyond the initial novelty value it lacks any worthwhile use that will make it a widespread practice, and anyone who tells you otherwise is at best following a hunch.

As anyone who's regularly read this site knows, I'm bullish about mobile: I think it is changing our lives and the society we live in, and will continue to do so in new and unforeseen ways. But jumping on every prank which new mobile technologies enable and declaring it important, without any evidence or research to back this up, only cheapens the really interesting and valuable work that's being done in this field.