Facebook held an official unveiling ceremony for its new data center in Prineville, Oregon, Friday. Local, county and state officials joined Facebook executives at the site of the 300,000-sq-ft facility in the small rural town.

The first 150,000-sq-ft phase is now online, with the second one, similar in size, expected to be completed by the end of 2011.

The unveiling came about one week after Facebook took a move unusual for the data center industry and published online design specifications for the servers running at the Prineville data center, and for the facility's cooling and electrical systems. The company released the designs through what it called the "Open Compute Project".

Facebook announced Open Compute about two weeks after environmentalist group Greenpeace publicly called on the company to "pledge to go green" by 22 April ÔÇô the date of Earth Day.

Greenpeace has been criticizing Facebook for choosing a location for the data center where power is provided by Pacific Power, a utility that uses coal-powered plants to generate a large portion of its overall capacity.

At the DatacenterDynamics conference in Phoenix, Arizona, on 13 April, we asked five data center industry experts one question: how useful is data released through the Open Compute Project going to be to the industry?

Here's what they said: