Spencer Ackerman in Washington and Ewen MacAskill in London:

“If your boss in the mailroom lies on his timesheets, the IG might look into it. But if you’re Thomas Drake, and you find out the president of the United States ordered the warrantless wiretapping of everyone in the country, what’s the IG going to do? They’re going to flush it, and you with it.”

While Drake’s case is well known in US national security circles, its internal history is not.

Major source
In 2002, Drake and NSA colleagues contacted the Pentagon inspector general to blow the whistle on an expensive and poorly performing tool, Trailblazer, for mass-data analysis. Crane, head of the office’s whistleblower unit, assigned investigators. For over two years, with Drake as a major source, they acquired thousands of pages of documents, classified and unclassified, and prepared a lengthy secret report in December 2004 criticizing Trailblazer, eventually helping to kill the program. As far as Crane was concerned, the whistleblower system was working.