1. If people drove the speed limit, there would be no need for privacy invasive traffic cameras. The blame there does lie squarely with the people who can't seem to get that, and who keep killing and maiming thousands of people every year.
2. There are very few benefits to cars going faster. If you want speed, trains are much more efficient at high speed. Fast cars are wasteful and dangerous.
Cars being limited to walking speeds in cities would be great. But failing that, I'm happy with the local groundrule: 30km/h if there's no bike path, 50km/h if there's a raised bike path, and 70km/h if there's a bike path that's separated from the road by at least 1 metre.