According to emails sent to users (I haven't gotten one), Dropbox is reporting that a bug in the selective sync feature has resulted in files going missing:
We're reaching out to let you know about an issue affecting Selective Sync that caused some files to be deleted from Dropbox. This problem occurred when the Dropbox desktop application shut down or restarted while users were applying Selective Sync settings.
Based on our investigation of this issue, we think you may be among the small number of users who were affected.
If you haven't used Selective Sync before, you can stop reading now because you weren't affected.
If you have used Selective Sync, we wanted to check whether your Dropbox may have been affected. We've set up a personalized web page where you can see if there are files that shouldn't have been deleted and try to restore them.
I haven't gotten an email, and I don't see any official confirmation on Twitter or the Dropbox blog, but Engadget did turn up a couple different reports so it is reasonably safe to assume that this story is true.
According to the emails, Dropbox is actively trying to fix the issue, and they are also making up for the lost files by offering those affected a free year of Dropbox Pro. There's no word yet on how many were affected.
Hmm. While I would like to snark on this issue, I think the more important story here is that we now see that you can't rely on the cloud services quite as much they would claim.
Dropbox, for example, offers PC apps which will let you sync certain folders on your PC to your account on their servers. This includes whichever folder you use for current work, but clearly that's not a good idea anymore. This bug has also shown that you shouldn't sync your main storage to Dropbox, either, but instead treat the cloud storage provider as an alternative to a local backup - an external hard disk, for example.
I know that no one has ever really said that you should sync your main working directory, but Dropbox does make it perilously easy to do just that. Clearly caution is in order.
image by Hugo Quintero