It applies to much more than you'd expect. I've always heard it referred to as the golden triangle, in which the three best options are presented.
In IT services (or web design, or whatever, really), my first exposure to it was "Good, Fast, Cheap; Pick any two."
I recently realized that with programming languages, it's similar, but not quite the same. Runs fast, has libraries, isn't totally frikkin braindead: pick one, if you're lucky.
Just now I realized that much the same applies to databases.