Unfortunately, many programmers take the opposite tactic: They shove optimizations in apriori of any testing or data, just because "they know it's faster", or "you should never do X". The result is often convoluted code. The Pareto Principle + Knuth's axiom (as shown by acqq) is the best route through such minefields, IMO.
You may not be one of the "many programmers" but I certainly have worked with enough of them over the years to know just how pervasive they tend to be.
it is a typical case of ideology (ie. following principles) approach clashing with the analytical reasoning over real facts/measurements/observations. People everywhere, be it science, programming, politics, religion, ... like to hide in the safe haven of dogmas. Whenever expressing of doubt is prohibited or frown upon - you immediately know what it is a case of ideology/dogma.
You may not be one of the "many programmers" but I certainly have worked with enough of them over the years to know just how pervasive they tend to be.