What is the primary danger if the rear wheel locks up and skids during heavy braking on a straight dry road?

1. The rear end may swing sideways (fishtail); if the rider releases the rear brake while the bike is sideways, a violent 'highside' crash will throw the rider over the motorcycle
2. The front wheel will lock at the same moment, doubling the stopping force
3. The machine will stop in a shorter distance than with the wheel still rolling
4. The rear tyre will lose air and the wheel will collapse onto the rim