It would be very difficult to establish a duty of care. Opes allowed clients to short sell (as do many of the bigger traditional margin lenders). So why should they not also foster short selling by external parties through the 'stock lending' system.
It is difficult to argue that they shouldn't foster short selling by lending stocks to hedge funds yet allow their clients to short sell stocks on market. It was just another way of making money (that may in turn have contributed to their downfall)
Even their new account application documents refer to being able to short sell.
