Posted by Kati Togliatti
My worst data nightmare happened when I was working in a shared folder on dropbox with someone else. We must have both been working on the same MATLAB code and the version I was working on had been saved over. All of my changes that I had made were gone and at the time I did not know in dropbox that you could revert back to older versions, so I thought the changes were lost forever. I only worried for a couple hours until someone mentioned you can find older versions. =] That is my most memorable data nightmare.
With github it seems like they really thought this issue through and I like that you can make pull requests to the initial author so that your own personal files do not get overwritten!