Results of a Wall Street Journal investigation published today show that many of the most popular Facebook applications have been transmitting personally identifying information—in some cases, even your friends' names—to dozens of advertising and Internet tracking companies.

The issue affects tens of millions of Facebook app users, including people who set their profiles to be completely private. The practice breaks Facebook's rules, and renews questions about its ability to keep identifiable information about its users' activities secure.

The WSJ says affected apps include…

Zynga Game Network Inc.'s FarmVille, with 59 million users, and Texas HoldEm Poker and FrontierVille. Three of the top 10 apps, including FarmVille, also have been transmitting personal information about a user's friends to outside companies.

Again, this means you may have been compromised even if you yourself didn't use the apps, but your friends did.

Facebook in Privacy Breach