If they get on and the crate is big enough I dont see why not :) I dont think I would leave any dogs unsupervised in the same crate though because if a fight did break out the victim would have no where to go :(
Depends on the size of the dogs and if they get on. If I have two in for grooming who are friends I put them in together but have never put any of mine in a crate at shows but in all fairness I dont crate now anyway as I find it makes the stroppy when they come out!!