A former Department of Education researcher who brought to light the loophole that allowed student loan companies, including Lincoln's Nelnet, to reap hundreds of millions in profits at taxpayers' expense, has filed a whistleblower lawsuit against those same companies. Jon Oberg, a University of Nebraska-Lincoln graduate and former aide to former U.S. Sen. Jim Exon, filed the suit in U.S. District Court for the Eastern District of Virginia. Nelnet is the lead defendant, but since the Lincoln student loan company settled its differences with the federal government more than two years ago, its spokesman said Nelnet considers the matter closed....