GroupCard, a startup that lets groups of friends sign and attach money to online cards, has been acquired by gift card company InComm.

Atlanta-based InComm says that its gift cards represented nearly $10 billion in retail sales in 2009. With GroupCard, it hopes to develop a stronger presence on the web, especially on social network Facebook.

GroupCard was founded in 2007. Founder and chief executive John Anderson said the service has now served “millions” of group greetings and gifts. In addition to serving consumers directly, it also lets merchants bring gift cards to their websites and Facebook Fan pages. GroupCard will operate as a subsidiary of InComm, with the team continuing to work out of Milwaukee and Palo Alto.

Anderson added that the acquisition is a sign of how dramatically the social gifting market has evolved in the last few years. When GroupCard started, there really wasn’t a market to speak of, but Facebook has really accelerated things, most recently with the “open graph” technology it announced last week at its f8 conference.

“What makes us so excited is [that out of] everything you saw last week out of f8, nothing there was more than eight months in the works,” he said. “It’s impossible to imagine what’s going to happen in another eight months.”

GroupCard was funded by the fbFund (itself a joint venture from Facebook, Founders Fund, and Accel), WordPress creator Matt Mullenweg, entrepreneur Yee Lee, and others.