Negligence is much easier to prove; it's the failure to exercise reasonable care. Willful misconduct is a much higher standard. You must intentionally misbehave. ... The high standard would clearly discourage many suits.
The question is how high the liability shield needs to be. I think 'willful misconduct' is too high. We usually use some kind of negligence standard in these situations. It would be very unusual that you could prove that intentional misconduct had happened.