Apple doesn't even lead the smartphone market (yet), RIM does. I'm sure they will catch up quick but RIM had 40% of the market last time I checked and Apple had 25%.
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.