I can't fail to notice that Seattle-based Wishpot is missing from the list (disclaimer: I work there). Wishpot Social Syndication offers a Facebook Shop with integrated wish list and a Twitter shop solution too, which enables merchants and brands to use Twitter to promote their products in a smart, non invasive (and not 'salesy') way. http://www.wishpot.com/social-commerce
We power more than 100 Facebook Stores (such as http://www.facebook.com/Guess.eu?v=app_2456371452... and users are not asked to add/allow any application, which - to me as a user - is a big plus.