Most are documents with inserted pictures, pieces of spreadsheets, Visio and Project charts. Insertion and deletion of the non-text elements appeared to significantly increase the chances of creating unreadable documents. Workarounds includes saving under different formats and removing history. I am counting my own problems as well as my closest coworkers.
As with Outlook's PSTs, there were no apparent cause for the corruption - it just happened.
I no longer use Word (back to Linux and LO for work), but I'll keep an eye on the Windows and Mac coworkers and reach you if I hear anyone experiencing these kinds of problems. We also have a consultancy working on a large project with lots of documentation and specs being generated as Word documents with Excel, Project and Visio elements embedded. I'll get in touch with them as I suspect they are the most likely to be hit by problems like the ones I had.
As for the other projects and teams, we have significantly reduced the use of Project as we moved our tracking to Jira and use Confluence to keep almost all project artifacts. Despite the fact we still use Exchange for e-mail, I dropped desktop software and moved completely to OWA, with Evolution doing backups over IMAP into a local maildir rsynced to a durable datastore.
As with Outlook's PSTs, there were no apparent cause for the corruption - it just happened.