Loss of control accidents
During adverse conditions it will often be noticed that it is the rear of a vehicle that loses traction first.
What the average person and some experts are not aware of is that there can be as high as 950 pounds or more weight on the front axle of their vehicle than the back. So a car that feels like a limousine on the front holds like a golf cart on the back
A 3000lb car with a weight ratio of 65% front weight and 35% rear weight will weigh 1950lb on the front and 1050 on the rear. After you use 10 gallon of fuel from the rear tank one of the front wheels has as much traction as both rear combined.
If you analyze single vehicle accidents you will find most of them had better tires on the front than the back or a very large weight difference. In fact the worst balanced cars have 4 times as many fatalities as cars designed with better balance. How are you going to tell how fast is too fast under these conditions when it is possible for a balanced car to handle fine on a slippery surface at 50 mph and an unbalanced car to lose control at 20 mph and both to feel the same to the drivers.
There are some good videos on the Internet showing how important the rear tires of a vehicle are. Also the Society of Automotive Engineers paper 2002-01-0553 shows any decrease of tread depth from new of the rear tires can contribute to an accident.

@Harvey

Thanks for the interesting comment regarding the f/r weight distribution in passenger cars. As a driver, I occasionally have noticed a lack of control in pickups with empty beds, and noticed that a car with a full tank of gas tends to handle better, but I always considered balanced weight distribution as more a performance factor than a safety factor - I guess autombile performance and safety are more closely linked than I thought.

@Darren By graphing the fatality rates of fwd vehicles compared to their weight ratios you will see that the difference between a full tank of gas and an empty tank is 20 fatalities per million registered vehicles.

@Harvey That's a very interesting statistic. What are the NHTSA's requirements for balancing weight distribution are, if they have any?

Is there a list online of "best to worst" cars based on weight distribution?

All the poorest models reported by Consumers Report Magazine have poor weight ratios 63/37 and over.