There is no economic damage requirement if you engage in explicit price or output fixing (which could be a verbal agreement). See: http://www.ftc.gov/os/2000/04

There is no economic damage requirement if you engage in explicit price or output fixing (which could be a verbal agreement). See: http://www.ftc.gov/os/2000/04/ftcdojguidelines.pdf http://www.ftc.gov/os/2000/04/ftcdojguidelines.pdf "Types of agreements that have been held per se illegal include agreements among competitors to fix prices or output, rig bids, or share or divide markets by allocating customers, suppliers, territories, or lines of commerce. The courts conclusively presume such agreements, once identified, to be illegal, without inquiring into their claimed business purposes, anticompetitive harms, procompetitive benefits, or overall competitive effects." Obviously small players aren't worth prosecuting but that's a different question.