CNN reports that Facebook has teamed up with Datalogix, a company that specializes in spying on you via "customer loyalty" programs. Datalogix monitors the purchasing habits of about 70 million American at more than 1,000 retailers.
Matching e-mail addresses or other data on "customer loyalty" programs with the info on your Facebook account, Facebook and Datalogix will be able to see whether you buy the crap that Facebook advertizes to you, and thereby work toward greater control of your purchasing behavior.
The solution to this sort of privacy invasion: Adblock Plus, Ghostery, and don't sign up for "loyalty" programs. (And pay cash when practical for purchases at brick-and-mortar stores, certainly for anything remotely interesting.)