Don't forget to block their web-wide beacons (a.k.a. "like buttons"), and lie about your birthday (useful information for identity thieves[1] -- remember how your bank asked for the last 4 digits of your social when you called them?). I still use them to keep up with some people I know, but with a somewhat fake name, a blank profile, and minimum searchability. I don't think using it unduly exposes me to identity thieves, creepy potential employers, and other not-Mossad threats[2]. I've used it since it required ".edu" addresses, and never clicked an ad, so I think I'm basically getting my money's worth.

[1] http://news.sciencemag.org/2009/07/social-security-numbers-a... [2] http://research.microsoft.com/en-us/people/mickens/thisworld...