You're in the middle of an Apple PR tsunami at the moment, but bear with me while I share this clip. It's the first part of the iPad launch. In particular take a look at the first 2 minutes and the way Jobs introduces the product's place in the market and it's core capabilities.
This approach to determining requirements is the right one, for all of us on every project. We need a context for our IT systems and business processes and it needs to be grounded in something that our client/customer/user values.
We'll talk more about Steve soon. In the meantime, invest the two minutes and reflect on how your requirements fit into their context.