I believe sky is the limit for fb's e-commerce.
In addition to all that is going on, do you guys remember when they launched a bidding game to own "photos" of people, where the highest bidder owned the photo at the end? Think about transforming that into an "ebay" phenomenon and monetizing with it. How easy and profitable could that be? ebay should be scared. How about fb comig out with owm email service?
fb is probably on its way to become a one-stop-shop, where you integrate socialization with email, shopping, file-sharing and storing (cloud computing), searching, mobile messaging, etc. This is a 1 billion customer-base stroefront and growing. With only 313 million people in the United States, this is the size of three times the US, with EVERYONE having an account on fb. The potential is huge, since they have the numbers. Advertisement along with e-commerce, Yes, this could dwarf Apple, Google, and Exxon.
I did not know they had their own email service - I do not know anyone with a fb email account.
They may not monetize specifically with the free email service, but they could send ads and offers via targeted email addresses.