To justify the kind of valuation it is seeking, Facebook is going to need to make a lot more money per user.
After waiting for so long to see the numbers inside Facebook's success, it's easy to be overwhelmed by all the new data we have about the social network and company. But there is one number that matters more than all the others:
In particular, I want to explain why this number matters so much to you as a user of Facebook, not just for Facebook at a corporate level.
To justify the kind of valuation that Facebook is seeking, the company is going to have to generate a lot more revenue that they currently do. Some of that revenue growth could come from getting more users onto the service. But Facebook has snapped up a lot of the easy users -- that is to say, people with the Internet who live outside of China. User growth will continue outside the western countries for a few more years.
However, even if Facebook gets to 3 billion users, if it doesn't increase its revenue per user, the company will only generate $13 billion in revenue per year, as analyst Trip Chowdry has pointed out. That's not going to justify a market capitalization of $100 billion. Google, for example, generated $38 billion in revenue -- nearly three times Facebook's hypothetical three-billion-user hypothetical -- and has a market cap of $190 billion.