De-registration should not be allowed, I agree with the others who have said that. It's extra complications for no reason and people should just be allowed to fall off the voter rolls eventually.
And for future reference, some of us are trying to play a game over here, so if you or someone you know is planning to quit playing, then please don't make commitments to your fellow players like running for a major office!
Not wanting to get spam PM's is reason enough to allow deregistering. It's better to have voter rolls full of people who want to vote than to have voter rolls with people who don't want to vote. It's also nice to keep track of who is actually active in the game.
Plus, why add unnecessary regulations just for the hell of it? This really isn't that big of a problem, so why make changes that could create more problems?