[Nrsolis]

Dont forget that a lot of trades didn't clear.

I read somewhere that something like 30% of trades used to fall through because of paperwork mixups and other problems before electronic exchanges.

How would you like to think you sold at a profit only to find out that the trade didn't clear and now you're in the hole because the stock bottomed out?

[veyron]

The worst part was May 6 2010 (the flash crash). The exchanges and SEC arbitrarily threw out a number 60%, and people who managed to buy at 59% discount got to keep their (very) profitable trade and people who managed to buy at 61% discount lost only one leg of the trade. The process was not transparent, at all :/

I know some people who made a boatload (all trades cleared), and others who lost a boatload (one part of their trade was cleared, but the other part was broken, and they had to go back and buy back at a very disadvantageous price)