I think the only speed limit generally not observed is 60 km/h in construction sites on the motorway, which seems to be interpreted by pretty much everyone as »Continue driving 80 km/h«. Otherwise, at least around here, it's just a few drivers that go faster than allowed but the vast majority keeps to the limits.
30 km/h and even 50 km/h are respected pretty much nowhere except where there are stationary traffic cameras. I ran across an article recently (can't seem to find it again) where 90% of German drivers voluntarily admitted to not keeping to the speed limit.
For most people, breaking the speed limit does not seem a big deal. Then they run over a kid and say "I didn't mean to do that"! Well, they did in a way - keeping to the speed limit is not hard.
