How is Apple a monopoly?
Last I looked Apple was in three major businesses: wireless phones, portable media players, and personal computers.
In the wireless phone business they are competing against Nokia, Samsung, LG, Google, Palm and Microsoft. Where is the monopoly?
In portable media players, they are competing against Microsoft, Archos Creative, Sandisk and others. In addition, there is nothing stopping any sizable company from building an music or video player tomorrow and selling it.
In computers, Apple competes against HP, Dell, IBM, Lenovo, and more.
Because their products run on proprietary software is not monopolistic. Most consumer electronics operate that way. My cable and satellite boxes are a closed system as is my printer, my telephone, my dvd player, my bu-ray player and so on.