The server side I think was written by benmachine as a way to end slow stalemeate games. But, I have never seen it used that way. I've only seen it used as a tool to help insure a win. Usually it is after an alien attack that severely cripples the hummie base then SD is called before the base can be rebuilt. Takes any hope right out of the game for hummies and I know a few players that don't play on SD votable servers because of it.
I've seen it used on the SST server and you can probably get more info at their forums-
http://forums.sstcentral.com/I see they are thinking about 66%-75% majority to pass SD as any team the has the most players can't force SD as a lame win. If it is no longer the simple majority to win the vote, then it may start to be used as it was intended.