Facebook has patented "Giving gifts and displaying assets in a social network environment." That's the official title for patent number 7,970,657). The patent was granted a little late though, given that the social network closed the Facebook Gift Shop last year.
The listed inventor is Jared Morgenstern, who started at Facebook in February 2006. Facebook filed for the patent on April 27, 2007 and was granted it on June 28, 2011. Here's the abstract:
A system and method is described for giving gifts via a social network and displaying icons representing assets that have been acquired via the social network. In various embodiments, the assets include real assets, digital assets, and virtual assets. Digital assets that have been acquired via the social network environment may also be displayed. In some embodiments, the assets are received as gifts or in trade from another user of the social network environment.
The patent doesn't necessarily prevent other social networks from offering a gift giving feature. It could make the process much harder, however, since Facebook has described social gift giving so that a purchase can be made known to participating parties as well as others connected to them on the site.
Most users on a social network want their activities to be known to others. That's exactly how Facebook made gift giving more social, and the patent will thus make it difficult for other social networks to do the same.
Facebook launched Gifts on February 8, 2007, allowing its users to send virtual gifts to their friends that appear on the recipient's profile. Gifts cost $1.00 and can include a personalized message. Facebook closed down its Gift Shop on August 1, 2010, saying that it would focus instead on improving other products. While you cannot give new gifts from the Gift Shop, the gifts you've already received on your Wall remain visible, and you can still view your sent and received gifts on your gifts page.