"Those who work as administrators of employee retirement accounts are required by law to act as ‘prudent’ trustees. The law does not make it clear if they are to be held accountable for losses accrued by their employees because of unwise investments. Regarding the case at hand, the employer encouraged its workers to invest most of their money in the stock held by the company."
http://www.jdjournal.com/2013/12/16/supreme-court-to-hear-case-regarding-401k-losses/#