this will be cool until smart contracts are introduced to end this:
From the Ethereum white paper:
"However, one notably interesting feature of this algorithm is that it allows anyone to "poison the well", by introducing a large number of contracts into the blockchain specifically designed to stymie certain ASICs. The economic incentives exist for ASIC manufacturers to use such a trick to attack each other. Thus, the solution that we are developing is ultimately an adaptive economic human solution rather than purely a technical one."
ethereum has the largest development community of any other crypto asset. I'm confident that if a company such as Bitmain wants to try to disrupt the ecosystem, the development community will respond.