If you're a MozyHome user and If you want to keep from thrashing your TimeMachine backup, exclude /Library/Application Support/MozyHome in the TimeMachine prefs. (TimeMachine pref, Other Options.) Mozy uses this folder for staging and tracking the uploads to its servers. So it's always being updated (TimeMachine will think it's changed every hour). This will push older backups off your backup drive earlier than otherwise. Mozy ought to add this exclusion automatically.