[wizofaus]

And yet some of the worst performance issues I've had to deal with were in code typically dealing will merely 100s of items, but using algorithms and slow network-based operations that caused everything to run sluggishly most of the time and not infrequently making the resulting user experience intolerable.

I do agree though that a lot of time is wasted on premature or even completely counterproductive optimisations for situations where the data being processed is too small to cause noticeable slowness in processing.