@hawkeye10,
One of the reasons I buy books online is because the B&N near me is so crowded I can never find a place to park, and they have a very large parking lot. They don't look like business is slowing down at all.
You can't compare video/DVD stores like Blockbuster and Hollywood to bookstores--those outlets are affected by changing technology as well as lots of competition. Why should people bother to go to those stores when the same films are often available on cable TV, or can be ordered from Netflix without having to worry about late fees? People can also purchase videos and DVDs at the chain bookstores, large electronics stores (like BestBuy), even drug stores, as well as online. The product is so widely available, you don't really need specialty stores.
The same is not true of bookstores. The main competition for the large bookstores would be online book sellers. The other main source of competition would be public libraries. But, those are about the only venues I can think of where you can find a huge selection of books.
I do think that economics is a factor. The price of books has risen, and currently, consumers are still keeping a fairly tight grip on their purse strings. All retailers are having similar problems, I don't know that the larger bookstores are especially unique in that regard.
The concept of a real material book--one with printed paper in a binding, that you can hold in your hand--is deeply rooted in the history of our culture and our social conditioning. Books haven't changed in form in centuries. If electronic readers become more widely used, it won't be for a while, and not until they substantially drop in price. And I still think that many people will still prefer a "real book" rather than an electronic device. People still go to movie theaters rather than watch DVD's, and some people will still want to go to bookstores and purchase books rather than use electronic readers.