Speeding is a real problem. Since mostly no one follows the speed limit, you may find it actually dangerous to drive at the speed limit.
What do you think, the best option is:
1) Always follow the speed limit, regardless of everyone else around you?
2) Move with the traffic, even if everyone is going 10-20 mph above the speed limit?
I believe that on regular roads (roads with stop signs, stop lights and crossroads,
you should always obey the speed limit. Unfortunately, on superhighways,
you need to keep up with everyone else.
I try to drive as close to the speed limit as possible, max +5 mph over. On the super highways, I have noticed so many times, people fly by me too fast; it is scary.
I might be wrong, but I believe it is still safer to be driving within the posted speed limit. The benefits of driving safe, outweigh risking your's and other people's lives.