I think that's a lovely idea - which doesn't work in reality. At some point someone will need to be cast out. That can't be done by peer pressure, because scammers, spammers, and griefers don't care about that.
Individual blocks also don't work because they leave unaware users open to being abused.
Sure, you could have a town council vote on a block, or have software which blocks a user for all if they have been blocked >=N times, but that's still moderation.