I wouldn't think there was a rule change per se, rather, a re-definition of the existing rule. In thinking back of some of the races, I remember many occasions when Michelin cars changed tires with what appeared to be only three grooves (due to wear) rather than the required four.
David Hobbs said something I agree with whole-heartedly. Something seems a bit askew when Schumacher, having won five races, only leads the championship by one point over someone whom has only won two races (before today's final results). The points system should reward wins more so than finishes.
But then, I think they should do away with refueling and go back to the days when a driver had to compensate for a changing weight and cg as the race wore on. And ban traction control. Make the driver have to actually use his right foot rather than just planting it like a digital on/off switch.
Is Schuey the best? Probably, but that Montoya is damn good.