See my proposal below. What I'm proposing would only require the installation of a Dropbox-like daemon on workstations and an Excel add-on that could make REST queries to a repository server. Otherwise, users of Excel just keep on using it, but their data is backed up, can be rolled back, and data in spreadsheets is available company-wide and can be integrated.

http://news.ycombinator.com/item?id=1430661