Bad, because it tells foreign governments what WE are thinking about them. Now if all cables from EVERY government were leaked, might be different.
Im not sure about the whole "we" thing... This is what the marxist F'ers in the fedgov and the state department are thinking. F 'em... I don't see this as an entirely bad thing.. There is potentially a lot here that can be used by us to assist in destroying our enemies. Namely the F'ing socialists in our country.