Re: They'll probabaly start doing it for real
" because it would be something I could take to court against the stupid speed limits, "
Speed limits have little to do with road laws which generally have "keep right when not passing" built into them. (or left, for places which drive on the left side of the road).
I've lived in a number of places where "slow people in the slow lane" bills have been proposed - and been trumped by someone (usually the police) pointing out that existing laws are sufficient.
A cop pulling you over and citing you for "failing to keep right" doesn't need to mention that you're holding up traffic if it gets to court.