Phil Windley quotes Ross Mayfield on the retail experience at Apple, and compares it to other places:

What Best Buy is missing is the fact that they provide no after market value add with their retail -- in comparison to buying and servicing with an e-commerce vendor. If I buy something in person I expect a person to be able to help me when things go wrong. At least during the manufactures warranty, and I might pay to extend that period with the retailer.

That's very true, and I think it explains why stores like CompUSA died, and why BestBUY is probably going to end up in trouble. If I can get the same lack of interest and knowledge for less at a website, why should I bother driving? At the Apple store, on the other hand, there's a ton going on, a lot of smart people who actually know something, and they encourage you to try the sample merchandise. Huge difference.