Even at the height of Microsoft's reign, you could still walk into a shop and buy a Mac. Just sayin'.
Five years ago you could have made an argument for Symbian being the Evil Monopoly in this market, but Apple/iOS has never been anything like a monopoly. People seem to confuse control over one device with an actual monopoly. They're not even remotely the same thing.
They have 90% of the mp3 market and 75% of the mp3 player market but that's still not a monopoly.
The only thing they could be accused of is a monopoly on non-crappy web apps. Pretty amusing.
(As of Q1, 2010, pre-iPhone 4, source: http://www.gartner.com/it/page.jsp?id=1372013)
No one seems to mind their MP3 player monopoly because the iPod was so much better than the alternatives.
Smartphones aren't expected to reach 50% mobile market share until Q3 2011.
Most people on HN have a really poor understanding of the global market. The US leaders are not the world leaders in the mobile space.