From the article, which even has a Wikipedia link to market maker: "Knight Capital Group is an American global financial services firm engaging in market makin

From the article, which even has a Wikipedia link to market maker: "Knight Capital Group is an American global financial services firm engaging in market making, electronic execution, and institutional sales and trading." Institutions and other big entities buy and sell stocks, in huge quantities. Someone has to execute these trades, and doing it electronically is infinitely faster and more efficient, and usually less error prone. And the platforms for doing this are therefore very "powerful". But "With great power comes great responsibility", and this company was manifestly grossly irresponsible on many levels, it was likely only a matter of time before something like this would kill them.