Another, and I think far more common case, where optimization for speed is rightfully desirable would be the code that drives a dynamic website. See perrin's impressive eToys success story for an admittedly extreme example; when you're facing a million pageviews an hour, you don't want your code to be wasting time, but even much lesser loads make speed an important goal. Nevertheless, of course, it does not override the factor of maintainability.

Makeshifts last the longest.