Among the most frequently cited reasons for keeping records secret: one that Obama specifically told agencies to stop using so frequently. The Freedom of Information Act exception, known as the "deliberative process" exemption, lets the government withhold records that describe its decision-making behind the scenes.
Obama's directive, memorialized in written instructions from the Justice Department, appears to have been widely ignored.
Major agencies cited the exemption at least 70,779 times during the 2009 budget year, up from 47,395 times during President George W. Bush's final full budget year, according to annual reports filed by federal agencies. Obama was president for nine months in the 2009 period.
Also see a report from the National Security Archive at George Washington University.