For months, hedge fund manager William Ackman has been one of the biggest cheerleaders for CEO Ron Johnson’s efforts to make over JCPenney. After all, the billionaire investor handpicked Johnson for the job. But Ackman’s cheerleading tone seemed to change Friday, when he offered a bluntly critical appraisal of Johnson’s performance. And who could really blame the investor, who sits on the Penney board? The biggest shareholder in the Plano-based department store chain, Ackman’s hedge fund is sitting on half a billion dollars in paper losses in Penney so far. On a happier note, he was wearing socks purchased at JCPenney when he made his comments.