just watched several of the recent World Cup Cyclocross races. the men's podium used canti's for the most part, the women's used predominately disc. during the races it was clear (when the wheels were obscured or too far away to see) who was using what by the screeching or lack of it. it's interesting that there is a decline from MTB (almost universal) to cyclocross (mixed) to road (almost nill). there are probably good reasons for this.

in any case, the progession clearly follows that of the environment in which the bike is ridden; from gnarly to comparatively pristine.