There's been great debate in the blogosphere about whether Apple's control over both software and hardware constitutes monopolistic behavior, despite the fact that many other manufacturers offer alternatives to the Mac in the form of Windows PCs.
Apple sued Psystar in July, alleging licensing and trademark violations and copyright infringement. Psystar countersued but saw that suit booted back by the courts. Psystar hasn't given up the fight, though, and the two sides are scheduled back in court next month.
Previous coverage: Does Psystar have a legit argument in Apple countersuit?