I believe people should strive to drive about 5 miles an hour over the speed limit. Even in Seattle, you won't get pulled over and I find that people who bump their speed up just that much tend to be more efficient drivers. Not reckless, just more efficient. They want everyone to get somewhere a little more efficiently, maybe get that extra car through the yellow light, whatever. However, couple things I will do in regards to my speed:
1. On any street with just one lane each direction, If I'm going five over and Speed Racer is tailgating me because clearly that's not fast enough for him, I'll slow down to about one mile an hour less than the speed limit, just to mess with him.
2. If you're at the front of a line of cars and going just the speed limit, or slightly under, yes, I will tailgate you. Why? Because you are holding up traffic. It's not hypocritical. If I'm behind someone going five over, no problem. They're cool in my book. But if you're driving the speed limit and there is a huge line of cars that wants take a walk on the wild side and go a few miles an hour faster, then we have a problem.