Do you trust Amazon S3 or Mosso Cloudfiles not to lose or corrupt your data?
rs: They are as safe as any other service provider. Ultimately, its always good practice to:1. Do your own backups2. Routinely test that you can recover from these backupsI would argue that point (2) is much more important than point (1). I do try to do that at least once a month to ensure that there aren't any bugs in the backups, including any missing parts of the infrastructure.For mirroring really large data, rsync is a viable solution.Edit: I do want to add that performing your own backups is really subjective and you might need to ask yourself - what's the cost to me/my business/my users in the event that I can't recover from backups and or my provider failed in their own reliability (for e.g. Carbonite)