Lifespan of Twitter
I could be wrong, but I don't think Twitter's going to be relevant in the US 5 years from now. It's too easy to replicate and difficult enough to monetize that I don't think they'll be able to.
Some historical context:
http://technologizer.com/2009/04/23/whatever-happened-to-the-top-15-properties-of-april-1999/
Geocities, Xoom, Friendster, MySpace, etc.
I'm especially skeptical of their success because of their meteoric rise. Too fast and there's not enough there.
