A few brief statements from the most powerful economist in the world apparently did more damage to the stock prices of the GSEs than two years of accounting problems and slumping financial results. Four days after Federal Reserve Chairman Alan Greenspan gave his opinion about Fannie Mae and Freddie Mac during a hearing before the House Financial Services Committee, Fannie’s stock had dropped 8 percent – from $62 per share to $57. Freddie’s stock took…