Alpha Raptor raises the question of who owns BLOG content? At least in the case of MSN Spaces, the author does. I think what we are seeing is law trying to keep up with technology. The intent of the MSN Spaces (at least according to MSN), is to give MSN the right to serve your content on their serves and make backups of it. If you think about it, those are copies of the bits you authored on your machines. And to keep copies of your bits, MSN needs the "right" to copy them. Or at least their lawyers are concerned that they need to explicitly ask for those rights from you. Quite a few companies do this (look closely licenses at blogger, typepad, livejournal, etc.). MSN merely gets more coverage because people don’t trust them :).
But from a technology perspecitive, it’s all rather silly. You don’t have to sign a waiver for every server your email passes through – but who knows how many copies of your emails are floating through cyberspace and how many servers are keeping copies. If you did, it would completely break how the internet works.