Some other obvious approaches mentioned down the thread: Charge for API access, charge for exceeding API limits, charge for exceeding certain follower numbers,

Some other obvious approaches mentioned down the thread: Charge for API access, charge for exceeding API limits, charge for exceeding certain follower numbers, charge (at various levels) for analytics, charge for feature sets inside things like Tweetdeck, charge for access to certain API functions and so on. It's hard to see $9 billion worth in these ideas, but that's only if we think in the short term. Twitter could be genuinely worth that in 5 or 10 years, but only if it focussed on customers, and that's only going to happen if the founders vision trumps the very short term investor greed.