Pownce, the free social networking and micro-blogging site that has been deemed as a competitor to Twitter, will be closing down on December 15, after it was acquired by blogging company Six Apart at the beginning of this month.

The service was started back in 2007 by Kevin Rose, Leah Culver and Daniel Burka, having been launched on June 27 that same year, while it became open to the public on January 22, 2008.

Culver, along with Mike Malone, who are Pownce’s engineers, are scheduled to remain with Six Apart, while Rose and Burka will become the company’s advisers.

As for the site’s users, they will be able to export their accounts, messages and media to other social networking services, whereas for their thirst for micro-blogging, it looks like Twitter will be the one to quench it from now on.

Since it was first released, Pownce was considered Twitter’s competitor, the two services offering users much the same features, although the former enabled them to also share photos, music, videos and events, unlike the latter.

Nevertheless, from the very beginning, it was clear that Pownce would not be able to outrun Twitter, many having foreseen its impending demise as early as it was rendered available to the public.

San Francisco-headquartered Six Apart is the software company behind the weblog publishing system Movable Type, the TypePad blog hosting service and the Vox Internet blogging service.

Presently, the company is encouraging Pownce users to join the Vox platform, as Chief Executing Officer (CEO) Chris Alden has stated on Six Apart’s blog.