It has been determined that understeer is the safest way to set up a car. If you dig into the bowels of the NHTSA data, you will find support for this.
If you look at the data and took a survey of what "average" drivers do in extreme situations, you would find that people over compensate for steering input. To balance that, a car set up to understeer will work better than one that is neutral or has oversteer.
This is the main reason Nader deemed the Corvair "unsafe at any speed" because of its inherent oversteer. This is also why people wreck 911's.
I know for a fact the balance in the Mustang's is set up to understeer, and would venture a bet that the Corvette and Viper are set up in a similar fashion. Fortunately, oversteer is a throttle away in these cars.