My friend thinks the exchanges also go down when assets "flash-crash", because it means normal users can get in to sell their assets. And when they can't get in, they also can't cancel their stop-loss orders, so it means a TON of assets are available to buy cheaply (by the exchange and/or certain VIP users/collaborators) as the value goes down. Then these are bought up, and the price quickly increases again, before the exchanges slowly come online again.<p>Therefore he thinks the people exchanges are either part of the "flash-crashes" (and buy up assets themselves, because they know exactly where most of the stop-loss orders are placed), or they get kickbacks from the whales manipulating the market, by giving them access to the database with all the limit and stop-loss orders.