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.