I'd be interested in knowing a few things:
1. What's the legal situation with this stuff, i.e. sending content (potentially offensive content) to strangers, particularly random strangers?
2. What are handset manufacturers going to do (if anything - if BJing is a passing fad it may not be worth the effort) to give control of the experience back to phone owners? Settings to accept certain media types only from recognised handsets? Marking handsets as "known" and thus safe to receive media from (i.e. a step below "paired")? Previews of content before you get it?
3. Given the current hysteria over porn and 3G, will operators feel the need to offer locked-down handsets which prevent the transfer of pornographic content (as if that's possible!), or at least impede it? How long before we hear of the first BlueGrooming (whether or not this stuff poses any real threat to children is a completely different matter - it's got many of the characteristics of a good old tabloid scare story)? What will the operators do about this - most of the measures I've seen proposed to counter this stuff operate at a network, rather than handset, level.
4. Are people using this sort of thing for anything more interesting than pranks? We've talked about Bluetooth at conferences and in installations before now (imagine a service which offers anyone who walks past your stand a video clip or URL for your product - but only the first time they're seen), is anything actually being done?