I know Mozy & Amazon S3 have multiple data centers, but does any of the other offsite/cloud backup services have multiple data centers? (i.e., Carbonite, MiMedia, CrashPlan, etc.)
Having multiple datacentres means nothing unless YOUR data is actually stored redundantly in different locations. And the only way to guarantee that would be to purchase a package that includes that service, which would likely cost a premium.
The other way to do this is to simply make multiple backups with different providers, provided that you can ascertain that provider A isn't just using the same back-end storage services that provider B uses.
And you're convinced back up services like Mozy and Amazon S3 don't have redundancy for all users/accounts by default?
I'm sure they have basic RAID redundancy, but for their cheap, entry-level plans I can't imagine they'd incur the expense of replicating your data to multiple sites.
Very good point. If so, then it doesn't matter which service I go with because I will definitely sign up with one of the cheapest home plans. The only deciding factor now is how fast they can ready my data in the event of a restore.