This is actually a very good point. I'm not sure that I have a solution for it at the moment. The lazy argument would be that information eventually leaks out, but that is not, in the slightest, a guarantee. I will have to think on that.

and has the resources to vote with their wallet

This outlines the need for a competitive free market. If a business is making an undesirable decision, then the consumer would have other options to choose from, or a competitor without those practices would enter the market to scoop up those who are disillusioned.

They are also incentivised to eliminate competition

The wilful direct elimination of competition is anti-competitive behavior, and is, therefore, incompatible with a competitive free market, and should thus be prohibited.