This argument really is not about whether to obey or not obey the speed limit. The REAL problem is that the punishment is monetary. This leads to all kinds of abuses in many jurisdictions.
If you simply took the money out of the equation we would be having a much different discussion. Speed laws would be enforced more equitably. Courts and cities could not then game the system as so many do now.
To all of those that say "Just obey the speed limit and there is no problem" Well not really. I agree your chances of getting a ticket lessen however Police are human, they make mistakes, Radar in the hands of an ill trained officer, not correctly calibrated is often wrong. Most jusrisdictions wont even countenance a challenge to their radar in court as to do so and win throws the entire system into question.
And lastly speeding itself is too much of an issue period. It has been made the bogeyman and cited (wrongly) in way too many instances as the "cause" of accidents. Accidents are comples sets of actions and decisions that cannot be reduced to a simplistic cause and effect.
Many countries have much higher speed limits than we do and fewer accidents per capita. It's our obsession with "speed" that is part of the problem.