A few days ago I upgraded my Adium Instant Messenger client on Mac OS X to the latest version. While I was working yesterday, I was being pestered by girls who really wanted me to visit _their_ webcam the whole day :(
I guess I am naive and thought only authorized buddies could sent messages to me. Apparently not. If you want the spam messages to stop, all you have to do is go to the Privacy Settings... in the Adium menu and select Allow only contacts on my contact list.