My big problem with online backup solutions is this. What happens if THEY lose your data or it gets corrupted on their systems?
If it's a serious company, it's a given that they should have a backup system in place in case these kind of things happen. Since you can't really tell, as everyone says they backup their users data, and when shit happens, it turns out they don't, you're pretty much f***** up.
The thing is, with the paltry upload speeds most people has, and the small storage space most services offer, online backup services are supposed to be used as secondary (or even tertiary) backup systems, never as the primary one, and only for really critical files that should be backed up in more than one place. As it is, I don't expect Mozy of McAfee or whatever to hold my entire musical collection or my ISP to be able to handle such enormous transfer with a reasonable upload time. I do expect them to be able to store copies of certain documents or key files, though.