Just read some a news article about OneCare. I like the idea, and I dont mind paying a subscription if I am getting something out of it - the Backup feature sounds like it could be interesting.
That said, I have four PCs at home. I would hate to pay 4x$60 to protect all of them. Today, when most houses have more than one computer, it would be nice if subscription-based apps would take that into account and allow people to pay just a little extra for each additional client instead of having us pay the full price.
TiVo does that already - you pay about 1/2 the subscription for each additional TiVo you have.