This article, originally published May 11, has been updated to note Pershing Square's closed-end fund is nearing negative returns, and not the entire return of Pershing Square investments since the firm's 2004 establishment. Video commentary and performance metrics from individual investments have also been added. There's no question billionaire activist Bill Ackman's hedge fund, Pershing Square, needs to chart a new course -- especially as the total return on its latest fund is closing in on negative territory.  Coming off its ugliest year in history, Pershing's closed-end fund posted another dismal quarter this week, detailing a host of flops in...