It's a new medium for communication. If it works, people will use it in new unexpected ways; if it doesn't, people won't use it. But there is a lot of excitemen

It's a new medium for communication. If it works, people will use it in new unexpected ways; if it doesn't, people won't use it. But there is a lot of excitement about new forms of real-time communication: twitter, recent friendfeed functionality, etc - so they may hit it right. You are enumerating the current segmentation of the space, which is useful if you want to determine where the product stays, but these dimensions are not set in stone. For example Wikipedia is about off the cuff writing that evolves into an official document, collaboratively.