This does exactly what it says on the tin, and is one of the most interesting web sites I've come across in ages. A near-limitless source of titbits; I'll be surprised if they don't make a book out of it one day...

SMS and IM: "Sure, you have presence, and a roster, but the store-and-forward mechanisms of SMS enable deferred delivery, delivery reports, and, above all, they don't impose on you. No "typing" notifications or popups to build awareness that the other person is waiting for your reply - in fact, there's no real pressure to reply instantly (at least not culturally, and not in my age range here, although I understand that younger people delight in ping-ponging dozens of inane messages between each other)."

Weirdly, I was chatting to a guy from a VC earlier today about exactly this. I'd never thought of it before, but I suspect usage of SMS and IM are rather different - one seems significantly more synchronous than the other. Can one replace the other - and will users want them to? I can't exactly see them running side-by-side...?

How Sal was Struck By Lightning: "If on the other hand a group of people do everything in their ability to propel towards an electrical storm whilst wearing gear that is most likely to encourage some form of interaction, then this sort of disaster can be expected."

Piracy worse than child pornography: "If you copy Craig David's CD you get ten years, but if you punch him in the face and pummel him into a seven day coma you will only get six. You are more likely to get the respect of the prison population with your six year sentence as well."