Onother aspect that I think should be considered here is the security of the info on those backups.
Does your db backup include peoples names, emails etc? If so than your backup should be as secure as the original.
So I do not simply download a db backup and store it on my computer unless I can protect it with something like winsesame (which I hope is secure - anyone else use this?). Otherwise I store those backups on another webserver where they are as secure as the original db.