Can You Build an e-Commerce Site/Can it Sell Inside Facebook?
Yes, and Yes!
There are several ways to build a store, but my favorite lately is an external platform (Con: Another Account/Login. Pro: Centralized Control and Automated Software Updates & Security), and it can even have your store INSIDE of Facebook (and not just a link back out to another site/store).
Pretty cool, huh?
The software for the store is much like a CMS, and is designed for anyone to be able to use it easily. It shows all Customers, Sales, Handles All Payments with PCI Compliance & Multi-Layered SSL Encryption, Processes Orders & even interfaces with all major Shipping Systems (UPS, FedEx, DHL, etc.). It can live in multiple sites/domains at once, and even does affiliate marketing. BOOM! Yes, there is a monthly cost, depending on how many items are in your store. TOTALLY worth it, IMO.