This is probably a suggestion that will never be implemented in Windows Live FolderShare, but I'd love to have the ability to support versioning. This drastically changes the service, tho. This would essentially be a personal CM repository. Perhaps FolderShare on Vista might solve this in part with the built-in versioning, but what I'm looking for is the ability to share that version history with multiple clients -- namely personal computers, but multiple users would be nice, too. Every time I think about this, I question whether or not it's really appropriate for the service, and I don't think I can say it is, but it is definitely a nice-to-have. For those who have the time and resources for it, I'd suggest using Subversion and TortoiseSVN; but FolderShare with versioning, a lot of this would be done for you. Perhaps this could be an additional service for the WL team. Hmm...
Edit: While not exactly version control, there have been a few suggestions the FolderShare team has received to keep a copy of files on a server. Additionally, there was a "check-in/check-out" suggestion. Together, these are the beginning of version control. I doubt we'll ever see it, but you never know.