For tuned cars, there is a recent come back of stretched tires on really wide rims. They give the car a very aggressive look, at a higher risk of blowing tires (and screwing up your rims). Obviously, there is no performance advantage, but its appearance is quite dramatic.
It was initially done to clear the fenders by stretching the tires and making the sidewalls diagonal. This style is very common on many VWs.
I took these photos at PIA in Tacoma while I was getting my brakes checked out. The first two photos are stretched while the last two are not. I personally prefer the non-stretch on my car for safety reasons, but I think the stretched tires are cool.
This is kind of like the same way I feel about motorcycles: Cool, but not for me.