That's a terrible idea: anyone can vote on a poll, which makes (alt) abuse very easy.
In some others forums that I am active on and that are much older than bitcointalk they have the option to make poll voting public, so everyone can see who voted for who. Would something like that be possible to implement here as well, forum software wise?
I don't think this will reach the top of theymos' Todo list. I've seen suggestions to add more control over which Ranks can vote, but that hasn't been implemented either.