That problem plays both on stop loss orders for longs and stop buy orders for shorts....on the long side someone could have a stop loss right now at $1 CDN....if some bad news hit after the bell today that resulted in RVX opening at 50 cents, oh well.  Nothing is really 100%....

I think its possible that it could be MMs who got caught off gaurd when buyers stormed in and bought the bad news of the trial failure.  I know that in the US Market Makers are exempted from positive determination rules when engaged in genuine market making activity, I imagine the same rules apply for Canadian MMs.