Business Week just published a piece on the potential for Facebook in online shopping. They focus on the role of Facebook Connect in enabling shoppers to post questions to their Facebook network before making a purchase.
It makes sense that this is the primary way Facebook Connect has been used so far in online shopping, since it's the easiest to implement. But it's just scratching the surface. The real potential is in bringing the social network to the shopping site (not the other way around).
For one thing, many people are hesitant to blast questions that they know are only relevant to a small portion of their network out to everyone. No one wants to be a spammer.
Also, most shoppers don't think of Facebook as the place to go when researching a purchase. The primary research destinations are merchant sites and content sites that address the product category.
Combine those two considerations and what you get is a requirement for a system that runs on the merchant (or content) site and tells a shopper which particular people can help them with their purchase decision, so only relevant people receive the shopper's questions.
If you sell online and this makes sense to you, check out the way TurnTo's merchant partners are using the TurnTo system to achieve exactly this. www.turnto.com/partnerlist.