Originally Posted by cyccommute

No, we don't agree. In a pitch over situation on a dry surface, the front wheel on a bicycle can continue to rotate. If you stop the wheel, the wheel doesn't slide but the rider and bike, i.e. the center of mass, continues forward, rotating around point 3 in the figure I posted. The hub allows the CG to rotate without the wheel converting from rolling friction to sliding friction. There is no "skid".

On a wet surface or even loose surface, the dynamics are going to be a bit different but not radically so. The front wheel may slide momentarily (we're talking fraction of a second) but the rider will quickly fall over because the front wheel has lost its gyroscopic ability to allow the rider to balance. The wheel will probably slip to the side because the rider is trying to compensate from the loss of the rotation in the front wheel and the bicycle and rider will crash rather than the wheel really "skid". You won't be sliding along on the bike with both wheels locked in the same way that you can slide a rear wheel.