It really comes down to the definition of monopoly and how a market is defined. If Microsoft wasn't found to have a monopoly in desktop operating systems, what they did wouldn't be illegal. Microsoft had north of 90% desktop OS market share at the time of the anti-trust suits. Does Apple have a monopoly? It depends on how you look at it. If the market is defined as iOS market share, then they definitely do (obviously). If it's defined as mobile operating systems, then maybe not. Currently iOS has a 59% market share in the US and only about 16% worldwide.