Im gonna wait a few more days and then buy a bunch of shares, the stock WILL go up and in a year or 2 will be $80-$120 a share. They platform they have, they will figure out a way to monetize facebook.
Typical ads will not work on facebook, they cannot compete with google because people go to google to find results in order to leave google.com, so google offers you some paid results which you may click on and they earn $$. whereas when people go to facebook they are looking to stay on facebook and they are not interested in clicking an ad about teeth whitening just because someone commented in fb that they whitened their teeth.
Facebook can perhaps make money on ads that just want to build brand awareness (think coke, p&g..) and do not care about actual clicks. They can also charge for a premium version of facebook that allows you to contact people who are private, similar to linkedins premium version.
I can continue rambling but ill spare you the pain..