Bubby
every market crash has been precipitated either from an increase in interest rates, or a decrease in available or access to cash !
mr hsp may in fact own (or have borrowed) the stock !!!!!!!!!!!!!!!!!!!!!!!!!! Super funds in Oz do this every day of the week ........as do people that buy puts or sell calls against an asset....
I would be much more concerned abt HFT ........
rgds
V_H