[UnoriginalGuy]

This is something I constantly have to remind people with "sync" solutions (Dropbox, rsync, robocopy, etc). Anything that mirrors or syncs has the potential to delete the SOURCE material too. That is what it is designed to do.

The responses I seem to get are "NOT if you set it up correctly!!" which is obviously true, while also somehow managing to miss my point entirely.

If you want to just one way copy something then use a solution that is ONLY one way (copy, xcopy, S3 backups, CrashPlan, etc). If you want to mirror/sync then keep a nice backup for when that goes wrong.

PS - Also make sure you know the "rules" a sync solution runs using. For example how does it decide when a file is deleting? Is it just looking at directory update time and lack of files? What if files haven't been synced yet but the folder gets updated?