Microsoft Program Manager Ian McAllister started the discsussion about this service, after posting some of the details on his Space a short while ago.
"The social shopping space is exploding with innovation and new user scenarios. Online/offline integration in the shopping space is a rapidly evolving area with dramatic potential to make people's lives easier. The innovation opportunities are unbounded."
One thing that has impressed me in the existing MSN Shopping service is its integration with MSN Search via the Shopping Instant Answers. This search for "MP3 player" for example, delivers back product information at the top of the search, which is something Google doesn't appear to offer yet. Combining Windows Live Expo with Windows Live Search and MSN Shopping could prove to be an easy and attractive way for users to shop online.