Amazon.com disclosed in January 2009 that it was the subject of a mysterious investigation by the U.S. Postal Service. Neither Amazon not the Postal Service said what the investigation was about, though some interesting theories popped up.

Now Amazon in its latest quarterly financial filing with the SEC says the investigation was closed last month and the company “settled for a nominal amount.” The amount wasn’t specified. I’m asking Amazon and the Postal Service for comment.

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