Talking about something with 2 other people is far less time intensive as typing the same out in an IRC chan or an MSN convo, and certainly would be more so if I stuck to typing everything correctly. In order to keep up with the natural 'flow' of the conversation I find it necessary to use shorthand and omit punctuation. Posting on forums I can't tell what everyone else is saying on the subject while I type a message, so there's a lot less urgency involved.
oh, and btw, iTouch mySelf atNight oO