The apps reviewed by the Journal were sending Facebook ID numbers to at least 25 advertising and data firms, several of which build profiles of Internet users b

The apps reviewed by the Journal were sending Facebook ID numbers to at least 25 advertising and data firms, several of which build profiles of Internet users by tracking their online activities. This doesn't surprise me at all, it was just a matter of time before ad networks and retargeters, et al, caught up to include Facebook. FB's "social plugins" and the cookies they leave laying around give these companies an incredibly reliable way of identifying unique users and mapping their profiles. Which is very valuable to them. One of the larger sites I run was recently approached by an ad network to drop a pixel upon user registration that would pair a user's email address with an identifier for unique tagging within their ad network. I declined for ethical reasons, but it was interesting nonetheless to see that this pairing is so valuable to ad networks, that they would pay for it separate from any display services.