friends

Facebook recently launched "Facebook Places". Depending on your settings any "friend" can find out where you are when you log in or comment. This is supposed to allow you to 'see' people who are nearby.

In addition, you or ANY friend can TAG you at an event and enayone who is checked in nearby among your "friends" can see your position highlighted

It gives the actual address & map location of where you are as you use Facebook. These days you can never really know who your "friends" are.