Scoble says:

Third, most marketing sites exist to build relationships with customers. You think most businesses spend all that money to only have you visit once? Yeah, right. The only way a company can become profitable is have you visit again and again and again. Look at Amazon. Unprofitable for the first few years in business, but now that they have lots of repeat and return customers they are profitable.

Yeah, Amazon doesn't have RSS. But, the bar is higher now than it was in 1998 (just like the bar in 1998 was higher than it was in 1989).

Actually, they do have RSS, and I use it - you can set up search feeds through Amazon that pump back RSS. It's quite useful, especially if you are interested in a niche genre or a particular author. For instance, here's a feed url that will answer a book search for "Alternate History". I do get some bizarre matches on that (I'm looking for stuff like Turtledove's WWII series, and I sometimes run across stuff like this - go figure).

How did I construct that search? Why, BottomFeeder has a wizard for that :)