This week's Economist:
[compared with Google] Facebook’s problem is more fundamental. True, the social network has some of the most extensive privacy controls on the web, but these have now become so complex—and are tweaked so often—that even privacy experts find them bamboozling. The company also has a powerful incentive to push people into revealing more information. Facebook generates most of its revenue from targeted advertisements based on users’ demography and interests, so the more data users share publicly the more money it can mint from ads. It may well be betting that users are now so hooked that they are unlikely to revolt against a gradual loosening of privacy safeguards.
Summary: Facebook prejudiciously assumes you want to share all your personal info, all naysayers are pushed to do so with frequent tweaks reacting to which is a bamboozling (sic), fiddly business for users. All so that that Facebook can mint more from targeted ads. Assume, push, bamboozle, mint. That's the Facbook business model in a nutshell.