I've been investigating and trying out Crashplan (I think the recommendation came from here). It kind of gives you the best of both worlds. You can back up locally on your LAN but also remotely to a friend or to the Crashplan servers. If backing up to a friend you can "seed" it doing a local backup and then transfer the backup somewhere else. Once seeded it only backs up differences. All of this can be done free and probably in return you could back up your friend if similarly inclined.

So far I'm pretty impressed and I've looked at quite a few "cloud" only solutions all with certain limitations that were frustrating.

Elephantdrive - slow uploads (they wanted me to break it into multiple uploads) and the software was using 600MB of memory/pagefile.
Sugarsync - just didn't get into it
Opendrive - limited versioning and backup type functions but economical
+ others

plus the many others that I reviewed but didn't actually install