Most people I know understand that they ought to backup their computer, and the majority of those don't actually do it; even the few that do backup don't do it very regularly.
Mozy provide such a service, a little backup utility will sit in your task bar and encrypt and backup your data to an online server. Files can be retrived by the utility or from a web interface. You get 2Gb of free storage, if you need more you can pay for it.
Disclaimer: I do get some more storage by referring people, but I wouldn't do it if I didn't think the service was great.Link