[greenyoda]

If Facebook becomes a middleman for Amazon (or some other retailer), they're going to want a cut of the transaction, so going directly to Amazon would probably get you a better deal (or at least fewer ads). And it's no easier to buy something through a Facebook app than through an Amazon app. (If people really want to type "buy me book X", Amazon can add that to their own app very easily.) So it's not clear what value Facebook would be adding here.

(I don't think that Facebook would actually want to be the retailer in this transaction - that would involve competing with Amazon at something that Amazon is very good at and Facebook knows nothing about, like warehousing, shipping, purchasing, etc... and requires billions of dollars to build. So I don't see Facebook having any role except being a middleman.)