Quick pointer to the story on mashups by Jennifer Schiff over at E-Commerce Guide, "The Lowdown on Mash-Ups". The article takes a very commerce-centric view of mashups, looking at where money is, or isn't, being made in mashups. It includes interviews with me, analyst Freeman Evans over at Jupiter Research, and Robert Yeager, the developer of eBay mashup Cooqy. Jupiter's Evans points-out that for many shopping mashup developers "You're basically a traffic arbitrageur or you're a new search experience that lets people discover products and then you may get a cut of the revenue, but you're really an affiliate then." Given that most shopping-related mashups use the Amazon API, eBay API or Shopping.com API, this rings true.
Holiday shopping to do? Shopping mashups continue to be quite popular, there are now 145 shopping mashups listed here.