Conceptually, I think Amazon’s aStore and Google’s Custom Search Engine are trying to achieve the same thing. Allowing the end users to customize and create manually edited, co-related pockets of well organized information.
Google’s CSE allows one to create a search engine that only searches among a subset of websites (web pages) making it more relevant for people searching in a specific area. In a way, it provides a way to create a vertical search engine for specific topic such as “vegitarian recipes”.
Similarly, Amazon’s aStore allows an affiliate to create a very specialized store. For example, here is an astore with books for learning indian languages.
Just like Google’s main website can provide end users to search for any information, Amazon’s website provides end users to search for any product. However, the aStores are manually edited and carefully picked so that they guide the users to concentrate on specific set of products.
Verticalization of any generic concept is always good.