Last Thursday, May 6th, the Dow Jones Industrial Average fell 1000 points in a matter of minutes. The House Financial Services Committee will be holding a hearing today to try to figure out what happened, but there are still many major unknowns, including, ominously, what caused it, who was to blame, and why the exchanges can't seem to get their stories straight. Heidi Moore looks at these questions.

Read it at The Big Money