Good cheap MiniDV tape degausser
 

I have to do about 10 swipes with the thing on both sides instead of the suggested 3 for VHS, but this degausser from TecNec works amazingly well in erasing MiniDV tapes. I think this is a good alternative from "blacking" them, which seems to just wear stuff down. Check it out:

http://www.bhphotovideo.com/bnh/cont...ughType=search

I know there was a discussion, and some issues in finding a solution that worked, so I'm just throwing this out there.