Surely an alternative and equally plausible story here is that the files were corrupted locally and Dropbox gave a 60-day window for them to be recovered.
However, having spent some time with people debugging a WebDAV client I suspect that this may be a remnant of Excel doing one of those complicated series of saving temporary and 0-byte files that MS & Adobe insist on doing. Perhaps it somehow hit a Dropbox sync at just the wrong moment and the 0-byte file was saved for posterity. This of-course would be a DropBox problem, but tricky time-centric syncing bugs like that are hellish to find and fix. The fact we don't see more is a testament to the brilliance of DropBox.
It's fairly unreasonable to expect DropBox to keep historical versions of your files for some arbitrary amount of time when you're not paying for the service...
On the other hand, it is not at all unreasonable to expect Dropbox to not sync 0-byte-files (if there was content in it before), which could also lead to the expectation that in those cases Dropbox would store an additional backup/send a message.
I think its unfair to blame Dropbox that they never mentioned 'Packrat'. Its clearly noted in their pricing page
https://www.dropbox.com/upgrade
Also, one should always periodically backup their files, so in the event of data corruption its possible to recover them. Corruption might happen elsewhere, not only defective dropbox client.
Never assume your data will be safe. There are always a million things that might go wrong. Just be prepared.
I recently accidentally removed my Dropbox folder and the client assumed I wanted to delete everything. I managed to pause it after only a couple dozen files were lost.
Navigating through the folders in Dropbox and figuring out which files i want to undelete was not at all obvious, since I didn't want to undelete anything not deleted in that accident. Having a simple "undo" button next to the event that nicely said "X files deleted" would've been a big time saver.
Packrat is nice, but if I have to manually fish out the important stuff instead of having an easy restore functionality, it's not much of a backup solution.
Author here: I'm not using DropBox for backups. I have a relatively slow connection to do that. I'm using DropBox for files that I need to be available on different computers/tablets...
I'm not blaming DropBox for not keeping an unlimited history (it's obviously my fault), I just believe that they should have taken the Client bug more seriously.
What I do: I have one partition for all my important stuff. I rdiff-backup it regularely to different devices like harddisks, usb-sticks and servers all around the globe. Feels pretty safe to me. Of course, if rdiff-backup has a bug or im using it wrongly, im toast.
I use SuperDuper! (http://www.shirt-pocket.com) to copy the SSD in my MBP to a disk image on an external hard drive once every day. The content of this hard drive is mirrored to another hard drive.
I also use Time Machine on yet another external hard drive, mostly for recovering individual files. And in case of fire, theft or some other sort of local accident, I have all my files stored with Backblaze (http://www.backblaze.com).
This backup-setup has yet to fail me. I had a chance to put it to the test last month, and a few hours after my computer initially refused to fully boot, it was up and running as if nothing had happened after restoring from the SuperDuper! backup.
> Turns out DropBox saves a history of all deleted and earlier versions of files for 30 days only.
I've found most people aren't even aware DropBox has this functionality at all. This is the first I've encountered someone who apparently knows about it, but does not know its limit.
Packrat, by the way, is available directly on the "Upgrade to Pro" page, and I think it has been the entire time it has existed.
> OTHER DEVICES AS BACKUP
> That didn't help either. The other devices were already synced with this defected version.
However, having spent some time with people debugging a WebDAV client I suspect that this may be a remnant of Excel doing one of those complicated series of saving temporary and 0-byte files that MS & Adobe insist on doing. Perhaps it somehow hit a Dropbox sync at just the wrong moment and the 0-byte file was saved for posterity. This of-course would be a DropBox problem, but tricky time-centric syncing bugs like that are hellish to find and fix. The fact we don't see more is a testament to the brilliance of DropBox.