I think we will see more of this. When MasterCard and VISA operated as an illegal duopoly the brands were interchangeable, but now they are competitors. They offer banks incentives to issue cards on their network, and some large merchants have made exclusive deals. I expect these programs will begin to filter down to medium size companies in the form of lucrative incentives that they can likely earn only by declining to accept other card brands. (i.e. MasterCard won't stipulate that they cannot accept VISA, but their quota will be set high enough that the only way they can achieve it is to favor MasterCard by declining to accept other cards, -or- by adding a surcharge on other network cards.)