The inflator that deploys the driver's frontal air bag in the event of an accident may rupture and spray metal fragments onto vehicle occupants. This can increase risk of serious injury or death.
On certain vehicles, the key can be removed from the ignition when it is not in the "off" position.
Power steering assist could be lost unexpectedly. Should this occur, steering ability would be maintained but would require much more effort.
While driving, the ignition switch can move out of the "run" position. As a result the engine would stall and the airbags would not deploy in the event of a crash.