yea, people would get hurt ALOT more in hovercrafts than they would in cars. Since cars have traction on the road, they tend to 'stick' more when they crash, so crumple zones have been designed to allow less of a drastic g-force upon impact. With 'hovercrafts' they will bounce off of each other so forcefully in a crash that the g-forces will be MUCH larger than those experienced in a car crash.
In addition, they require ALOT more fuel to run, as you can't just take your foot of the gas and coast, you constantly have to be providing enough force to actually lift a multi-ton vehicle off the ground.
You suck at ideas ;-)