Charlie linked to a brief post I hurled up about instant messaging and SMS, and it's gotten me thinking: what's in this for the various parties involved? Who gains and who loses if I can see presence info for, say, the folks in my address book?
What am I more likely to do if I see a friend is unavailable? Send a text, or not call at all, instead of calling and leaving a voicemail. What do operators earn from a leaving-voicemail/checking-voicemail/call-back sequence, compared to what they earn from an SMS/call-back or SMS/SMS? I bet there's someone somewhere in the organisation scared of cannibalising existing revenues who'll put the boot in.
This is one of the places where new operators like 3 or the MVNOs can really do new stuff: they don't have a history or entrenched views, and there isn't someone working somewhere in Billing to throw a hissy fit when your new service - which customers might love - is going to take revenue away from their empire. (Not that I have anything against anyone who works in Billing - God shall be their judge, not me)
And what about users? How much would I pay to expose presence information about myself, and to see presence information of my friends? And how do we manage the inevitable conflicts of interest: what happens when you want your boss to see you're busy, but your friends to be able to contact you? I suspect that managing this stuff on a mobile is a fairly tricky interface problem.
Meanwhile, here's a use case where IM is great and which operators have failed to deliver on: the 3-way (or 4-way, or 5-way) horrendo. That is, where you want to have a group chat. I think there's money to be made from anyone who solves the "synchronising a group of mates on a Friday evening" problem...