how come mark zuckerberg is so rich when facebook is free ? how do they make money on it ?

[Slim Shady]

He is rich because of his stocks in Facebook, which is still hugely overvalued imo. Their revenue last time I looked was quite pathetic for the user base they have. Their share price has dropped since they were offered(until this month apparently) probably for the exact reasons as your question: how do they make money from their users? Targeted ads is one thing but they have so much more, data on users which maybe only google can compete with, once they get an idea of how to capitalise on that it will be huge which is what investors are waiting for I guess.

For a long time I thought google sold user data, they don't. It is their bread and butter, their market edge, facebook is likely the same.