Apple doesn't even come close to having a monopoly.

Microsoft most certainly did have one during the browser wars, and were leveraging it to get people to increase IE marketshare.

With Windows on the desktop, you didn't really have much of a choice but Windows if you were going to use pre-package software, play games, or do business. With the iPhone, you've got tons of competition - Android, RIM, and WP7. If you don't want to work in that model, nothing forces you to, either as end user or VAR.