I might pay for a Premium twitter account if I got past the Fail Whale - but a question: wouldn't picking any revenue model put an upper-bound on Twitter's evaluation? I mean, if the Premium account is $5 a month, and you know that 2-5% of users purchase it, then it's pretty easy to figure out what Twitter's revenues are, as a basis for a more scientific evaluation. Maybe, because the current investors have set the evaluation so damn high, they will actually SHUN a lot of the revenue-generating ideas that don't justify the inflated evaluation, thus dooming Twitter to never quite have a model, or to be sold.