We recently flew to LV through SouthWest. On our return in Chicago, the flight was overbooked. They offered to refund your original cost + $200 and would get you out on the next flight. We would have flown free.
Still kicking ourselves for not volunteering, but our daughter was with us and she had to get back. We noticed all flights were Full everywhere it seemed. Of course this was during Spring Break. By the looks at the airports, business is booming.