I just found this new start-up, JadedPixel. They are building an e-commerce application:

Shopify is a hosted e-commerce application designed from the core to be simple, fun and beautiful.

They keep a blog detailing the building of Shopify and their search for investors.

Building a hosted e-commerce system sounds tough (every merchant will want to make customizations to the way the software works) and dangerous (if they go down I lose money). I guess (and hope!) they have thought of these issues and have solutions.