Goose..
Do you mean only shares held in margin accounts..??
If so ..no...all shares held in all acounts(Except RRSP,Trust accounts of any kind and US IRA,401K accounts) can be shorted,if you have made those arrangements with your broker...it is the margin account shorters that really sweat because if the short goes the wrong way the broker can call the WHOLE margin account ,not just the shares shorted..so shorters with margin accounts cover fast...
I believe he was talking about the margin players shorting..It is so good I'm going to listen to it again..Did you like it and did it open your eyes..??
It did mine..
Portee