It might be getting harder to have a guaranteed seat on your airline. I have personally been lucky and never have been bumped from my flight, but I would imagine it being a horrible experience.
Due to airlines cutting back flights and having fuller flights, the chance of being bumped is getting greater. The NYTimes reports that 343,000 passengers have been bumped so far this year. That is a lot of comp flights, meals and hotels that airlines have to pay for, wouldn’t seem to make economical sense.