[cmelbye]

Please don't mislead people. Ad buyers do NOT receive any private information from Facebook users when they run an ad. They tell Facebook what kind of user they want to see their ads, and Facebook shows the ads to those particular users. There is no exchange of information.

[aroch]

Pretty much what Beagle said. Targeted ads on Facebook are the social network equivalent of a spear phishing email. It's trivial to target a very specific set of even just one individual if you've done your research and then follow them around the web

[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).