Carbon ration cards
From the Daily Mail (via Ahmed): Every adult in Britain should be forced to carry 'carbon ration cards', say MPs.
Everyone gets carbon credits, but they can be traded.
My first reaction: The transactions costs seem like they would be especially high, isn't this why "money" was invented? Wouldn't a carbon tax be more efficient (yes I realize it wouldn't raise awareness as much, but isn't that a good thing).