Disregarding the incredible business opportunities that are available to Facebook (Credits, taxing Connect more broadly, targeted offers based on very detailed demographic profiles), the fact of the matter is that Facebook may be able to one day identify purchasing intent not only before Google, but before the user themselves identifies that intent.
If Facebook knows that you recently got married, and that you just surfed over to a baby website (equipped with the "Like" button), you might be intending to have a child, even if you're not yet pregnant. They can start selling you a daily-deal on diapers before a kid exists to soil them.