A large amount of inverts in the diet can cause problems with the frogs and their livers. I understand feeding mice to a snake because they can't eat ANYTHING ELSE.
I just don't think it's a very humane idea. If it could eat something else and still get a good nutritions I think it's pointless to kill those animals just for the sake of it being 'awesome'.
It doesn't seem very animal caring to me personally.
(I'm not trying to flame or anything!! I'm just in a personal bad mood and bah, I want to stab things.. :[)