Secondly (specific to this instance), Twitter is Second Life for the "cool" geeks (what's the emoticon for sarcasm?). Which is to say, though not as nerdy as 3D, it is an interesting indicator of future interaction patterns ("follow the alpha geek"). But, its never going to be a interesting business, and the early pioneers will likely not stand the test of time.
An ex-VP of Business Development of one of my endeavors once said "Our goal is to have a business model that you can't disprove in a finite amount of time." (I probably should have listened to him - but that's a story for another day)
So here's my new axiom for the new economy (I'll warn you in advance that its not as pithy as my former colleague's):
If you have a Chief Revenue Officer, you might be a jack-ass.