>Well, they do end up infinitely small you know!
That is the "classical" black hole theory, assuming the star that collapses doesn't rotate. Later studies on rotating stars came to quite different conclusions.
Quite often it is assumed that it is very hard to tell what happens within the event horizon, and the event horizon itself is taken as the "size" of the black hole. Still quite small, though, even for the supermassive black holes in the core of a galaxy (millions or billions of times the mass of the sun).
Hilmar.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)