Microsoft’s Windows Live Messenger instant messaging network (formerly MSN Messenger) is currently blocking messages with urls that contain *.youtube.com. Tietokone, a Finnish IT publication reports that this applies to messages with links to *.mediafire.com, too.
WTF, how did the people running Windows Live even come up with such a lousy idea? I’m guessing the explanation, if one ever will be given, will be related to spam/trojans/phising or whatever the latest security scarecrow is. I’m not willing to speculate whether this is some conspiracy to undermine Google owned services, and this would certainly not be the best way to perform such an operation.
I also verified that this is true with BitlBee. The filtering appears to occur on the server side, not in the client.