I've watched Notch code numerous times (mostly on Ludum Dare streams) and he's strongly in the always keeps moving camp of developers. He thinks as he goes and isn't scared to backtrack or rip stuff out when he changes his approach.
I participated in Ludum Dare this time and live streamed for a little bit, but the constant knowing that someone was watching me was really distracting so I eventually turned it off and was more constructive.