to be on the sho would mean that a negative influence is being pressured on the stock price... so there is a point in time that it is 'bad' for the sharholder...
HOWEVER, if an event occurs that would create an undeniably positive influence on the stock, then potentially, that 'pent up' negative influence could be removed violently as the inefficiency is taken out very rapidly...
(and THAT, of course, would be very GOOD for shareholders... and very bad for the shorts...)