PayPal has launched a Facebook application designed to let users of the social networking site send money to each other.The application, named Send Money, features a greeting card component for accompanying the money transfer with an e-card containing a message, photos and videos to mark occasions like birthdays and anniversaries."In a world that's turning increasingly to social media, we are giving our customers the flexibility to send their money to whoever they want, whenever they want and for whatever 'occasion' they want," wrote JB Coutinho, a senior product marketing manager at PayPal, in a blog post on Thursday.Cards are posted to recipients' Facebook Walls, although the message is kept private. Users can also opt to just send someone money, without posting an e-card to their Wall. Almost 80 percent of active PayPal users are on Facebook.This move by PayPal reinforces the growing link between social media and e-commerce, in which the social graph is being used for a variety of shopping-related activities, such as product recommendations from friends and special-offer targeting by merchants.Juan Carlos Perez covers search, social media, online advertising, e-commerce, web application development, enterprise cloud collaboration suites and general technology breaking news for The IDG News Service. Follow Juan on Twitter at @JuanCPerezIDG.