Here's a potentially disturbing Facebook.com security bug. Let's say you've posted some photos for your friends to see. I'm not on your Facebook friends list, but I am friends with one of your friends. Our mutual friend posts a comment on one of your pics. That comment and a thumbnail of that pic will show up on my Facebook home page. I can click it (entering your album) and see the full picture as well as all the comments. But it doesn't end there. Once I'm into your album, I can walk through all the photos in that album as well as comments.
Hey Facebook... I hope that's not a feature. Hopefully it is a bug you're working on fixing. In the meantime, I'd be careful about what you say and post on Facebook. Of course, that's probably good advice for the web in general :)