Citi trader error causes European stock markets to lose €300B in minutes

- Why was a single trader able to cause such a move? What does that say of the ability of the market to handle manipulation by a single player?

- If a market participant had some in place orders, for some crazy values. Will all the orders be honored?

- Does this market includes a circuit breaker?

- Another fat fingering incident like this, even if it's an automated trade, and how much real and possibly extremely large losses, could come again on the direction of the tax payers?

It's is fake money that is fake lost. From the article:

A mistake by a single stock trader caused a €300 billion ($315 billion) flash crash in the European markets on Monday. The US-based Citi group acknowledged on Monday night that one of its traders had triggered a sudden, sharp fall in European shares in a matter of minutes, with an equally rapid recovery afterwards.