Apple has cracked the problem of a computer for everyone else. iPad. I've now demoed and recommended the iPad to several people as a replacement computer to their desktop or laptop. It has been a fantastic success for them as their main use cases are email and the web. These people fall into two broad categories. CEOs and Moms. Both are essentially light computer users that are often confounded by traditional computer interfaces.
One curious side effect of the iPad being good enough is that they never plug it into their personal computer. Their desktop or laptop is collecting dust in the corner never to be used again as there is no need. It's heavy, complex to use and takes minutes to boot. Why would you want to use it?
The problem is that the iPad relies on a traditional computer. It's actually required to use iTunes in order to activate. But the real problem is that unless you plug the iPad into a personal computer from time to time the operating system is never upgraded and it's never backed up. The latter is bad for users but the former is bad for Apple. Users never get to experience the latest features and are subject to existing bugs. Apple isn't able to migrate their customers to mitigate support costs and open up new functionality for updated or related products such as Apple TV.
The iPad needs to break away from personal computers at some point. The latest rumours suggest the iPhone 5 is being released along with cloud support in the form of a free MobileMe account designed to help store and sync your content. Apple has positioned the Mac as the centre of your digital life over the past several years. I don't doubt that it will continue to support that role for years but requiring a Mac for AppleTV, iPhone and iPad limits the usefulness of these peripherals.
Sooner or later a friend or family member is going to get burned for not backing up their iPad often enough. Bad news for them and for Apple.