You'll want to read this from the top of this topic folder:
Sticky: Announcement 11-18-08Basically, I can't tell you why, since I don't know. I can tell you that any subscriptions will be fully supported through their term up to the end of 2010. Renewals and new activations will probably be disallowed by the end of 2009 and subscription purchases will likely be ended some time between 6/30 and the end of 2009 via the official Microsoft download/activation process.
-steve
Microsoft MVP Windows Live / Windows Live OneCare Forum Moderator