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. Howe

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.