I'm not one to complain about a free service like Facebook, especially when it works so well at keeping people in touch, but... I was very surprised to discover that links I view (but don't like) in my feed appear in friends' timelines. All I have to do is click the link, and that fact is potentially broadcast to all my friends. Doesn't that seem a bit too revealing?
Let me make it clear:
All potentially embarrassing of course, but what about the security considerations? What if the link is malicious in some way? You get hit by a dodgy phishing attempt for example, but so do all your friends! It seems like a recipe for disaster, as malicious links go viral.
I've had a look through Facebook's privacy settings, but there is nothing to stop this behaviour.
Update: This isn't quite as sinister or widespread as I first thought. It turns out that a Facebook app (The Guardian) I'd authorised a while ago was the one that posted as me. It's worth looking through your list of installed Facebook apps, and decide if you can trust them to 'post as me'.