[beagle3]

Not directly, no. But at least in 2010 (last time I did anything to do with ads), you could buy the ad according to your demographics on facebook, and then plant a cookie to correlate to other sources of information.

So, yes, I was able to use facebook to mark specific people (by buying an ad that targets them), and then follow them around the internet by participating in real time bidding on their views.

So even though facebook does not directly sell that information, you don't have to be very smart to indirectly "buy" it from them (and AdNexus and friends).