Many sync software offer multiple types of sync (e.g. MS SyncToy), and many are extremely cautious before deleting multiple files. Dropbox didn't do that. Yes,

Many sync software offer multiple types of sync (e.g. MS SyncToy), and many are extremely cautious before deleting multiple files. Dropbox didn't do that. Yes, I failed to totally understand how did it work, as I deleted one of the root level folders and expected it'd not sync a folder which is not there on the local machine, but one of the duties of software is to prevent or try to reduce common human errors.