> And you can't pay Twitter's bills on the 0.1% of users who'll pay $5 a month.

I wonder do their bills exceed $5 million a month. (I know, you pulled numbers from nowhere. I'm only making the point that they have an absolutely enormous userbase[0].)

[0]http://thenextweb.com/twitter/2011/09/08/twitter-100m-users-...