If you and I, a couple of presumed nobodies, agree to have our respective companies work together exclusively on a thing and maybe trade some money and services, then that's something that can usually be legally just fine.
But if you or I are operate a monopoly (whether a natural monopoly or an artificial monopoly) and we make the same kind of exclusive deal, then: That may not be fine. We have laws (like the Sherman Act) that can restrict this sort of thing only if a monopoly becomes involved.
And to be clear: It's generally OK to have a monopoly (good fuckin' job, mate! you totally own your market! all the spoils for you!). But it's generally not OK to use that monopoly status in an anticompetitive way.
But if you or I are operate a monopoly (whether a natural monopoly or an artificial monopoly) and we make the same kind of exclusive deal, then: That may not be fine. We have laws (like the Sherman Act) that can restrict this sort of thing only if a monopoly becomes involved.
And to be clear: It's generally OK to have a monopoly (good fuckin' job, mate! you totally own your market! all the spoils for you!). But it's generally not OK to use that monopoly status in an anticompetitive way.