Usually people would have the mentality of always trying to get a full market share while leaving your competitors in the dust. Today I was just reading about how another person actually shares his customers with competing businesses and as a result they often get more business that way. Essentially, if one person is out of stock then they can refer them to the other business.
He described it as like having a franchise network power without actually having one. In many ways this can be like friends sharing things amongst each other and building a strong community within a particular circle. Usually it is about who you know in order to succeed and this can definitely be a good way to do it assuming everyone is trust worthy. I suppose it can show confidence too as you have to be pretty sure about your position in the market to freely help others as well in this aspect.