Another good reason to keep your apps updated:
“The company has confirmed that a bug in an older version of its desktop apps could lead to files being deleted permanently, without the user’s knowledge or consent. The problem is related to Selective Sync, which allows users to only synchronize some important folders across machines.” – Neowin
Anyway, at least dropbox is trying to recover the lost data and reimburse the users who lost stuff. It’s not clear, though if that’s only for folks who had paid storage (i.e. refunding money for subscriptions) or not. Folks are getting a year’s Pro subscription service free. That counts for something, at least. They also say that the newer versions have fixed the fault.
Also, this didn’t happen to everyone, so check whatever you stored there. Also, use some redundancy: Most important stuff if in the cloud, also on a removable HDD. Personal stuff (financial, etc.) NEVER in the Cloud.
Source:
http://www.engadget.com/2014/10/13/dropbox-selective-sync-bug/