The UFC has really made waves recently with its business tactics and could be opening itself up to litigation under the Sherman Anti-Trust Act.
The Sherman Anti-Trust Act has been a staple of the free markets for over 120 years now. Two sections really define behavior that kills competition and a free marketplace.
Section One deals with two entities engaging in anti-competitive behavior. This generally involves price-fixing, market-division agreements, etc.
Section Two deals with one entity acting alone that has acted to either increase or maintain its monopoly. Being a monopoly is not necessarily illegal, but being a monopoly and engaging in anti-competitive behavior is.
Microsoft recently came under fire of the Sherman Anti-Trust Act because it was hindering competition in the Internet Browser software market, AT&T was split up due to violations of Section Two, etc.
Google is a perfect example of a monopoly that does not engage in anti-competitive behavior, in fact, Google actually encourages it.
The UFC recently though, has really begun to act in ways that are very anti-competitive.
These practices include counter-programing other promotions, banning specific clothing companies from advertising, threatening to ban any fighter who signs an agreement to appear in the EA MMA video game, having fighters sign exclusive image rights agreements, and supposed recruiting of other organizations' fighters.
Given the market share that the UFC has and the track-record of anti-competitive behavior, I wouldn't be suprised if an anti-trust lawsuit is waiting for Zuffa down the road.