I'm not sure if there's some kind of big power struggle going on right now, but obviously MSN is blocking strings containing "www.youtube.com".
It started by me finding a funny youtube video (who didn't?), and tried sending it to a friend. Message back was that "Message could not be sent because of a network error". Some Googling brought up other people with the same problem.
Is this the first of a series of power struggles on the big Web 2.0 sites? Will Facebook block out LinkedIn links. Will Google (the owners of youtube) not link to Microsoft content? Interesting times we live in, indeed.
Update: Seems it works again, where they trying to block some virus? Is blocking a major site the best way to do that? Was there really a virus or where they merely displaying their power? Will we get to know more? Not likely.