Here's a new one:
Oosah
1TB (yes, TERABYTE) of online media storage! I guess I could backup my music there to have access everywhere, but I use Simplify Media for that. The iPhone interface is pretty slick, though. A native client with local sync would be even better!
OK, it doesn't really fit into the backup thread, since it only does media files, but it's still an interesting piece of the puzzle, since media files tend to be the bulk of people's data. In combination with another solution, it's an interesting idea.