I'm waaaaay too ADD to read through all these posts this morning, but I will say that we need speed limits, but speed "limit" is more of a misnomer. If you're going under the "limit," most people deem you as going too slow, thus making it more of a recommended, or targeted, speed than anything else. On straight, flat roads like those in the plains states & parts of the mid-west (Ohio... ) speed limits are there basically to make sure someone getting on the road & getting up to speed isn't gonna get blown up by someone else already going a buck fiddy.
However, here in twisty land, I think the limits are very important. I use the speed limit & recommended speed signs to judge the severity of upcomming turns & twists. If I'm blowing through a section of wide sweepers at 80 then come around blind corner that isn't rated but would be rated at a 30 mph corner then I'm gonna have way too many adjustments to make in that short a period of time.