I can tell you this. i have heard of brokerage firms going bust and not having to pay up on their shorts.
I'll see if I can dig up some cases in bankruptcy court. If you know anything anout BK court collateral means bupkis becasue assets are never what they seem these days. First the courts get paid. Then the lawyers get paid and if there is anything left over the creditors get paid. That is fact.
Man you are touchy and why didn't you leave a message? I would have called you back.