4. Proprietary Problems
Both AOL and iTunes don't work well, or at all, with outside services. AOL's instant-messaging protocol is fully able to communicate only with the Google Talk instant-messaging service. It can't do the same with the IM platforms from Microsoft or Yahoo.
AOL also has a walled garden of tools and content accessible exclusively to users of its software. Its proprietary nature has changed a lot from the days when you could check your AOL e-mail only through AOL software. But you still need to use its software to access many AOL chat rooms, premium multimedia features, and parental controls.
iTunes has its own propensity for proprietary features. Want to play a non-iTunes video on your iPod? To do so for free, you'll have to hunt down a solid third-party tool for converting videos. Conversely, iTunes doesn't work with Microsoft's Zune digital audio device or other MP3 players.
Updated: Also, despite Apple's recent decision to sell some DRM-free songs, most iTunes tunes still play only on iPods, a couple of Motorola phones, or a computer with iTunes software on it. (DRM-free songs from iTunes, which used to cost 30 cents more than regular US$0.99 purchases, now are similarly priced.)
5. Lowest-Common-Denominator Attitudes
Just as AOL made getting on the Internet stupid-proof in the 1990s, Apple's iTunes made buying and downloading digital music and adding it to your iPod easy in the early 2000s. That ease of use comes with trade-offs. For example, iTunes does not allow you to add mobile-phone ring tones to your iPhone that you didn't purchase from Apple. And, as previously mentioned, iTunes won't transcode videos automatically — you have to use third-party software.