Facebook is an ever-evolving beast and its next evolution is called the Facebook Graph Search. The latest round of changes that you'll see (or may be starting to see if you signed up for the preview) as this is slowly rolled out will be access to your information that has previously been private if one of your friends doesn't have his or her privacy settings locked down. The long and short of it is that once this is made available to everyone (as it stands now there is no "opt-out" option), anything your friends have tagged you with or have liked as it relates to you leaves you wide open to snoopers. Remember the instacreeper I wrote about? This is going to put that guy on steroids, and it should rightfully freak people out.
A less than savory example: I did a search for "my friends who like Ashley Madison" and, well, I got more info about people I know than I ever wanted to. (Ashley Madison is the dating site for married people who want to have affairs.) "My Christian friends who like Satan" is another interesting one, and a third search for "my friends who like doing heroin" and well, you see where I'm going with this. "My North Carolina friends who like marijuana reform" certainly reinforces the statistics and news that says 58 percent of N.C. supports medical marijuana. It goes on and on.
In anticipation, here are a few good links to get you started and will help you help yourself before the Facebook apocalypse comes and crushes a lot of people's online glass houses. That said, the best way to prevent your dirt from surfacing via Facebook Graph Search is to, get this, not have any dirt. Not such a novel idea, is it?
EFF.org: How to Protect Your Privacy from Facebook's Graph Search
Huffington Post: Why Graph Search Could Be Facebook's Largest Privacy Invasion Ever
ABC News: Facebook Graph Search: Now Is the Time to Go Over Your Privacy Settings
If you have 45 minutes to watch the long-winded Facebook announcement about this tool, here's the video:
Get to it all ye Facebookers with skeletons (and the rest of us who don't but want to protect ourselves on principal)!