Facebook is whoring itself, its called user initiated advertisement. Companies pay big money so they can make fan pages of their products and then have it advertised. After that, any time a person does ANYTHING in those fan pages, its blasted all over you social newsfeed. The click through rate is astronomical compared to regular advertisement links and its not nearly as in your face because on the surface, it just looks like word of mouth advertising.
On top of that, the geo targeting they can do is retarded considering how much information they put up. You want to advertise to only single women who enjoy tennis between the ages 22-24? You got it.
Edit: I should note that they have some pretty big restrictions on how many times an ad can be shown and what not, but facebook basically took the bot one step further and made each user their own personal advert bots.