Consider monopolization, where one of the elements is monopoly power (generally determined based on market share). If we can define markets based on the degree to which core customers would refrain from switching to other products in response to a price increase, then basically every brand with a devoted following is a monopoly! The market consists of it alone, since core customers would not switch in response to a higher price, and the producer is the single seller within that market — a textbook monopolist.

Take Starbucks, where I’m sitting as I write this. There are many, many people (I am not one of them, by the way), who have a MUCH stronger preference for Starbucks coffee (and perhaps the whole Starbucks experience) than the cofee (and coffee experience) at any other coffeeshop. Starbucks would not lose their business if it raised its prices substantially. Does that make Starbucks a monopolist? Surely not.

If inframarginal preferences define markets, leading to an abundance of “market power” for antitrust purposes, then antitrust prosecutors and plaintiffs will become the all-purpose policemen of the business world. That’s because any firm with monopoly power (and there will be lots of such firms under the D.C. Circuit’s approach), runs afoul of the antitrust laws if it engages in unreasonably exclusionary conduct, which is notoriously difficult to define. Freed from having to make any sort of rigorous showing of market power, antitrusters can go around attacking all sorts of vigorous competition, labeling it “exclusionary conduct.” Given the vagueness of that concept, they’re likely to have a number of successes. To borrow another classic description, antitrust will once again be, as Robert Bork once described it, “in the good old American tradition of the sheriff of a frontier town: he did not sift evidence, distinguish between suspects, and solve crimes, but merely walked down main street and every so often pistol-whipped a few people.”