But I'm not crazy (at least, not completely). I've just been taking a lot of online quizzes lately--you know, the ones all over the Web promising to reveal your IQ, personality traits, or celebrity resemblances. Aside from discovering my inner Sleeping Beauty, I've also learned something important: These quizzes are about far more than providing users with enlightening or entertaining information.

The Real Deal

While Web quizzes may be fun to take, they're also a powerful tool for companies to collect your data and even your money--and often in ways you might not notice. We'll get to the spooky stuff in a moment, but let's start with the simplest method of quiz-based marketing: advertising. The very nature of a typical online quiz requires you to divulge all sorts of details about yourself. Those tidbits of info are like nuggets of gold for advertisers craving a way to connect with you.

"The big trend is about engagement," says Debra Aho Williamson, a senior analyst with eMarketer. "These quizzes are getting people to pay attention to ads."

Paying attention, it seems, is almost a requirement: Aside from being carefully targeted at your interests, the ads are often in-your-face and impossible to avoid. Take, for example, TheFreeIQTest.com, a quiz I found via a text ad on Google. By the time I clicked through the 105th "offer" (aka advertisement) it threw in front of my results--no exaggeration--I gave up without seeing the results of the quiz.

"There's a clear annoyance factor, leading people to one thing, then at the last minute bait-and-switching them," Williamson says. "The challenge with this type of advertising is walking that line between people wanting it and people wanting it to go away."

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 sells them to drug companies looking to market medications.

Bigger Issues

Unwanted advertising, unfortunately, is only the tip of the iceberg. Some online quizzes will surprise you with required payments or purchases before you can access your results. While the requirement may be in the fine print somewhere, it's often not in a place you'd easily notice before beginning the process.