It is the same princliple, applying an XSLT transformation on the XML data published by Amazon.com. (Now I just have to learn what the heck is XSLT!)
For example, here are the top selling books at Amazon.com using the keyword.... (drumroll please) "weblog".
BookWatch (web page view):
It just might mean it does not really manner how the standards are devised at a particular site if there are public tools like this to transform it to compatible flavors of RSS or whatever else we can dream up to connect content with.