Why I never answer quizzes in Facebook

They can't guarantee your private info is safe.

From NPR.org's 2nd part of their 4 part series:

What people often don't realize, Conley says, is that these quizzes are applications. Just like games and other entertainment, they're programs that run in a user's Web browser.

"You think that all you're doing is answering a few innocent questions," Conley says. "But in fact, you're opening up your entire profile and almost all your personal information to whoever wrote the quiz."