It ruins the friendship and trust. One concrete example is the unfair transaction encountered by my cousin. She used to hire Company A to supply them Rhums but to her surprise, the other store akways received 1 pack containing 6 Rhums free, so she shifted to another supplier and later the supplier knew the reason from the other store that always receive I pack Rhums. They're cheating.Yeah it will bring unnecessary competition that might not be healthy. So it is good not to double cross at all