Well, it doesn't seem that obvious, at least not to everyone, because several times I've seen people rewrite things to make it O(1) when it was actually slower for the vast majority of cases (or even all cases).
> In many cases it's guaranteed to be small or small-ish.
And in many cases it's assumed to be small, but not guaranteed. That's where the trouble lies.
A classic example is Windows using a quadratic algorithm for arranging desktop icons that caused severe performance issues when users had many icons on their desktop.
Well, it doesn't seem that obvious, at least not to everyone, because several times I've seen people rewrite things to make it O(1) when it was actually slower for the vast majority of cases (or even all cases).