We’ve all seen them. Quizzes that promise to tell you how smart you are, whether you have a dirty mind or which Star Wars character you’d be (Luke Skywalker, in my case).

If you’ve spent much time with these things, you know they are generally quite simple, some with as few as a half dozen questions. How much can you really learn about someone with six questions?

Quite a bit, it seems. Here’s an article at PC World by JR Raphael that looks at how companies use these quizzes to gather personal information about you for advertising purposes.

The ads can follow you long after you click away, too. Just look at RealAge, a detailed quiz that assigns you a “biological age” based on your family history and health habits. The site, a recent investigation revealed, takes your most sensitive answers–those about sexual difficulties, say, or signs of depression–and, if you opt in, can send you e-mail messages about those conditions. Those messages are, in some cases, sponsored by drug companies looking to market medications for those conditions.

Maybe you don’t care if marketers use your desire to figure out which super hero you’d be. And then again, maybe you should. Isn’t it amazing how eager we are to surrender our privacy in exchange for a few minutes worth of entertainment?