Just discovered a pretty random 'feature' on Facebook Chat.
I don't know how many of you use facebook's relatively new chat feature. It's a small box in the bottom right of the browser. Anyhow, yesterday I logged into my account on the iMac downstairs. It's a private PC that only me and my family use, so I left my facebook account logged in downstairs.
Earlier this afternoon, I spoke with one of my friends on the facebook chat. We had a short conversation, without any confidential/personal information being discussed - but a chat nonetheless.
Anyhow, I just turned the screen on the iMac, and the facebook page was still up in Safari - and to my horror, the chat that I'd had upstairs on my own PC was shown up in the bottom right of the screen in the Safari browser. Therefore, I can only assume that what I typed upstairs was broadcasted to my logged in account realtime - without me knowing.
Normally when I log into a site, I expect it to log me out elsewhere - especially with Instant Messenger.
Watch out for the same thing catching you out!