It is FAR more efficient to short futures or buy put options on indicies.
You want leverage? Buy short-dated out-of-the-money puts on S&Ps - interestingly, the Sep series expires this week.
I dare say trading records are going to be examined VERY carefully.
BTW, I am NOT short.
The only massive disruption I can think of was the Long Term Capital Management debacle, and they destroyed themselves in the process. (Then there was Nelson & Bunker Hunt, and they bankrupted themselves too, didn't they?)