No, I don't agree. People don't put 500K in with a bookie. We do. We do this because we know that money is safe as soon as we exit the position.
No trader is in for unlimited risk. The ability to NOT trade, mitigates all risk, accept the individual trades *WE* deem safe enough to expose ourselves to.
If you can go through the kind of hell MF Global put thier customers through, then we are exposed 100% of the time, with no way to get off and sit on the side. I just don't see how the markets can function like that.