Facebook suspended several popular apps, including Familybuilder's Family Tree app and nearly all apps by LOLapps Media of Gift Creator and Quiz Creator fame over "passing Facebook UID to a 3rd party advertising company called Rapleaf," which could use Facebook IDs to put names and faces to the anonymous consumer data it collects.
According to WSJ, "Rapleaf transmitted this data to a dozen advertising companies, including Google's Invite Media. All 12 companies involved in this leak say that they didn't keep or use the Facebook ID numbers. Rapleaf's defense is that no names were shared, and that UID were included accidentally. It looks like Facebook is taking your privacy -- or the company's valuable data, if you're cynical -- pretty seriously this time."
Facebook says on the issue; "Recently, it has come to our attention that several apps built on Facebook Platform were passing UID, in a manner that violated policy. In most cases, developers didn't intend to pass this information, but did so because of the technical details of how browsers work.
[…]We're talking with our key partners and the broader Web community about possible solutions."