I decided to dig in and research the current landscape thoroughly, both to better understand the lay of the land and to save you the research hassle.
It was only a matter of time before Facebook and e-commerce would converge. Until a little over a year ago, only storefronts existed on Facebook, where merchants could display and promote their products and, with “Add to cart” buttons, imply e-commerce functionality.
(Important Update: Facebook no longer supports FBML. Please refer to the articles on Facebook iFrame.) One of the most popular FBML tags is fb:visible-to-connection. A favorite of marketers, this FBML tag allows a Facebook page to show different content to fans and non-fans. When a non-fan clicks the Like button – viola! – the non-fan content disappears and the fans-only content replaces it. As a method of motivating a visitor to become a fan of your page, this can be very effective.
This FBML tag is often—and erroneously—referred to as a “hack”; however, it was created by Facebook to do exactly what it does: ”to display the content inside the tag on a user’s or a Facebook page’s profile only if the viewer is a friend of that user or is a fan of that Facebook page.”