In a recent Ad Age article, a number of marketers revealed to the world an undeniably creepy new detail about the data-mining industry: Facebook is keeping tabs on which of their users is pregnant. Information which is then used to target advertising. Because brand loyalty begins at conception.
It's not difficult to see how they could do it, based on the amount of commentary and in utero pictures one usually sees on FB. Facebook unfortunately refused to reveal the details of this practice to Ad Age (like Google and most of the other data-gathering industry, which discloses very little), instead acting as if there are parts of the Facebook page that they consider "off-limits."