Think about it- let's go to some park and lay out some ribbons in a few zig-zags and a few circles. To make it require another $1500 bike with different tires, bars, frame geometry (like anyone really understands frame geometry anyway) let's throw in a few logs and rocks so they will have to dismount. Now let's make a rule that says no dually bikes because if we do that everybody will want to ride their mtn bikes and we can't have that. And if the course is to smooth they will ride road bikes or heaven forbid- "cross bikes".
First of all Mike, you can ride any type of bike you wish in a cyclocross race - you just have to remove bar ends. Cyclocross is an old sport, the bikes evolved
prior to the existence of mt bikes, therefore, they look quite a bit like road bikes. I am, primarily, a mountain bike racer. Cross is furiously athletic (jumping, dismounting) and helps me stay in shape over the winter. Plus, having a cross bike allows me to have a fast road bike that can also chew up dirt roads, light single-track and such. Toss on slicks and you can race most of them. You certainly don't have to dismount, some riders hop the barriers and ride the climbs. Oh, I won a cross race on a "dually bike". I also like bmx, downhill and dual slalom - every one is quite a bit more fun if you have a bike made to match the discipline.
