I think that around the time that I noticed that OneDrive's Excel Online finally got the ability to sum cells by mouse-selecting a range of cells, rather than manually specifying the range, that is when there were some hiccups at Microsoft and a day's worth of changes were lost. Looking in the revision history of the file (File > Info > Previous Versions), there was not even a trace of any changes made on Nov 19, 2014. So far this data loss appears to have only affected Excel Online and not OneNote, which I also frequently use. I use Excel Online mainly for ease of use with my Windows Phone; many of my other are in Google Drive. I hope the worthwhile changes Microsoft is making don't further adversely affect Excel Online. So much for cloud backup. Note, a quick search on Google and Twitter did NOT seem to indicate any problems with Excel Online.
