Premature Optimization on WikiWeb
Premature optimization is the root of all evil.
In Donald Knuth's paper Structured Programming With Go To Statements, he wrote: "Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. Yet we should not pass up our opportunities in that critical 3%."
However, Premature Optimization can be defined (in less loaded terms) as optimizing before we know that we need to.