I went to a house to look at some electrical problems and the first one I seen was, In their 100 amp main electrical panel, there was no bonding bar from the ground bar to the neutral bar, and there was neutrals from feeder wires connected to the ground bar. I know the only reason why you would separate the grounds and neutrals would be if there was a disconnect before the main panel, but was not and don't need to be because they are back to back, so what my question is what kind of harm could that cause.