The problem, at the core, appears to be one of misaligned incentives meeting societal level trust.
Do you blame the fox for eating your chickens, when you yourself placed him in the coop, to protect them from marauding wolves? Or should you blame yourself for foolishly trusting a fox with your chickens?
It is all well and good to blame the "evil" finance guys for all your problems. But it is much too simple a solution.
We, as a society, have given these people the power to do such damage at such scale to incredibly important societal systems. We must design our systems such that we never entrust anyone with the ability to manipulate public common systems (markets/government). This is because no matter how "noble" people say they are (they may be sincere!) - abuse will inevitably become rampant - it is human nature. This is also why communism/Marxism and libertarianism can't work in reality.
> Power corrupts. Absolute power corrupts absolutely.
We need to stop trusting people - period. This is why, at least in the US, we have 3 branches of government, so that each one will check the other out of self-interest and balance possible abuse/corruption (not perfect - but pretty darn good!).
An easy fix would be to require all big traders in any market to not have a sell-side department at all - the Chinese Wall in financial institutions is a complete farce (as a cynic once told me: If it can be exploited - it will be exploited).
Other examples would be to have all trades rate limited that they can't lock up the market at any one point in time - similar to DDOS measures used by websites (click too many times and you just gotta wait). You shouldn't be able to dump a $4 billion short position on the futures market over just one second, let alone over an hour. You must rate limit entry and exit of trades so that we can smooth market dislocations and reduce the thundering herd problem found in extreme volatility.
Anyone else got suggestions?