Apple is a prominent user of DRM--Digital Restrictions Management.
You aren't free to install the applications you want on your iPhone and iPod Touch. Apple is the final arbiter of which applications are allowed and which are not. Contrast this with your home computer, on which you can install any program you like. The iPhone won't play patent- and DRM-free formats like Ogg Vorbis and Theora, either.
Apple argues these measures are for "security." Security expert Bruce Schneier says that "With iPhone, 'Security' Is Code for 'Control'."
Apple keeps a record of everywhere you go with your iPhone.
Apple uses DRM to prevent Macs from playing video on "unauthorized" displays.
Apple sell DRM-laden movies and TV shows.
Apple uses their control of both the iPod and iTunes software to unfairly block competition from competing music players, or competing applications.
Apple does not publish the set of conventions, or "API", through which the iPod and iTunes communicate. Rather, they change it constantly. In many cases the only goal of these changes is to force customers to only use Apple products with iTunes and vice versa.
When the Palm Pre (a smartphone that competes with the iPhone) included iTunes compatibility, Apple shot back with an automatic software update that broke the Palm Pre's iTunes compatibility. The update didn't tell users that it could break compatibility with their new phone; the only warning was buried in an Apple tech support page a few weeks earlier. When Palm fixed the problem, Apple broke it again. They made their own software less useful, hurting their own customers, just to enforce lock-in.
Apple abused the DMCA (legislation which makes it illegal for you to assert your basic rights by breaking DRM) to keep people from even discussing how to make other software players work with the iPhone. Apple tried to use the DMCA to force Bluwiki, a host of public wikis, to take down a public discussion of how to make other music player applications compatible with the iPod and iPhone. But iTunes compatibility isn't illegal under the DMCA, let alone merely hosting a site that discusses it. It took seven months (during which the page was effectively censored) and the threat of an EFF lawsuit to make Apple back down. Apple feels so entitled to the lock-in that DRM provides that they try to stretch DRM legislation to cover cases where it doesn't apply.
Not that interoperability would solve the real problem, since both of these pieces of software are proprietary. But this same tactic excludes free software users (and was used in the past to target free software users specifically).