Protecting your privacy in social networking sites

From NYTimes.com, funny but pretty darn scary:

Attention on the issue was brought about with an outraged post on AOL’s Download Squad blog about a man who, while using a third-party app, saw an ad for a dating site that, to his surprise, was dressed up with his wife’s picture. No, she wasn’t looking for a lover. Her picture had been usurped by an ad network in the employ of a third-party application developer, which she believes was a quiz app.

Originally from EFF.org newsletter.