Whether large or small, monopolies have been illegal in the U.S. since the first half of the 20th century, which is why the government now oversees the mergers and acquisitions of companies. The idea is that no one company should be capable of extreme pricing (or other competitive advantages) by virtue of wholesale market domination. While we Americans still believe in corporate Darwinism, we reject this principle if it's exercised in ways that harm consumers and workers. To paraphrase John Stuart Mill, the freedom of your fist ends where my jaw begins.
To we simple veterinary folk, however, the word "monopoly" probably seems more relevant as a classic board game than the intangible threat it implies. After all, competition is alive and well in veterinary medicine. But as our industry confronts increased corporatization and consolidation, the word has acquired a new resonance for many of us. Monopolization is an issue we're just starting to recognize as it creeps quietly into our daily lives.