People around here ride knobbie mountain bieks all the time. I had one blow past me the other day while I wa riding to work. =) I bought some tires and parts from a guy that lives less than a block from me that commutes on what is proabably would be called a monstercross with tubeless tires. He only rides about 1 mile to university campus, but he loves the plush ride and being able to roll over everything.

Years ago I rode someting even as bad as a 24 inch Huffy mountain bike back and forth to college which was probably 4.5 miles each way. In fact all that time I only had 1 bike that wasn't a mountain bike and that was a Panasonic road bike that I paid $10 for and didn't really ride much before I lent it to a friend and it got lost or stolen or both.

I 'll add that I have a friend that rode over 3,500 miles last year all on a Giant montain bike with knobbie tires and alot of that time he was car free. He will probably hit 4,000 this year even though he and his wife bought a car.