It is, of course, very early to speculate on the cause of the tragic crash at Reno. A disciplined examination of photos, however, reveals a possible clue.
This photo was shot by Tim O'Brien of the AP and Grass Valley Union just a moment before the crash. A sharp-eyed Russell Farris spotted an elevator trim tab that is either missing or severely deflected. If the trim tab was deflected downward at such an angle, the elevator would have been forced upward with a great deal of force. This would severely pitch the nose upward, likely with enough force to overpower even the strongest pilot.
In such a scenario, the pilot would push forward on the control stick with all his might to arrest the pitch rate. If he was unable to do so, the nose would continue to pitch further and further upward until airframe failure or ground contact occurs.
It's important to bear in mind that at the speed he was flying today, a relatively small control surface deflection would have resulted in an abrupt and extreme load factor ("G-force") on the pilot, making recovery that much more difficult.
Here's hoping the reaction of the public and media doesn't put an end to the Reno Air Races. You can bet that none of today's victims would have wanted that.