Pretty funny, although I personally don't enjoy having that kind of stuff done to me (nor do I do it to others). It just seems a bit much to make someone feel paranoid for two weeks just for some stupid prank.
I just found it really clever and funny. He did stop once he saw his roommate was past the "that's really weird" stage and started being paranoid. I would do that to my friends but everyone I know uses addblocker.