At my first job (small shop with three devs) they were using VSS and it was so much of a diasaster that I took it upon myself to prepare a sizable document on why do we need to move off of VSS to something like SVN. Manager's response was something along the lines of "I don't trust those fancy merge algorithms, unlock-modify-lock is the way to go". I couldn't convince him otherwise, he wouldn't even agree for a itsy-bitsy pilot project to test the waters.
Having exhausted all my options, I did two things. First, I "Got Latest" of the entire repository. Second, I wrote a smallish script that would overwrite a single random byte in a random number of files inside the VSS database directory and scheduled it to run overnight. Of course it would self-destruct upon completion, so that no traces were left.
The next morning, VSS was on it's knees and nothing could be done. Turned out we had no backups.
And this is how we "migrated" to SVN.
1: Yes, I know that TFS supports git repositories. But I have the same issue: Convincing management that this might be a good idea.
2: Actually I consider TFS's source control part worse than VSS. While VSS was a hack, TFS is sold as 'enterprise' software. And it's unbelievably bad (again, only talking about the source control part and leaving out all the other things it can do. Maybe some are less half-assed than the source control part is?). Given the choice I'd pick CVS over TFS.
Take a little look at this: http://www.highprogrammer.com/alan/windev/sourcesafe.html
At least with NO version control, you know you're not protected. Bad version control, such as VSS, gives a false sense of security that you're protected when you're really not, which is worse.
We ended up buying perforce which saved our arses but the days of VSS were dark days indeed.
I put ClearCase on an old version of my CV, because I was nominally the sysadmin in charge of it for six months. I still get calls about it. Those last ClearCase shops, they're getting desperate.