There's been a lot of controversy about facebook's new privacy settings (including a huge donation-run open source alternative startup called Diaspora that looks like it might end up competing with facebook. Cool stuff.)
Mostly, the concern is that facebook can change its settings without you easily knowing it. And that those settings are hard to understand. Lots of people are accidentally sharing their facebook information with the world and not knowing it.
There's a free tool called Reclaim Privacy. You drag it to your bookmark window, log into facebook, then click it. It evaluates your settings and lets you know if any are insecure. Then you can choose to change those if you want, or keep them. I read reviews by some other tech people whose opinions I trust and they liked it. So I installed it and tried it out. Works pretty well. You get a window like the image on the left, and then you can adjust your settings if you want to.
If you were worried that it was a password-stealing scam, don't be. It's pretty neat.
Now, if you want to spy on people who don't realize that their settings are wrong, you can go to Youropenbook.org and do some searches on things that people are (usually without realizing it) sharing with the world. Don't do that with kids in the room, unless you've tried it first. Some of the "recent searches" and suggested searches - and facebook postings - are pretty raunchy.
Warren