This isn't unheard of at all, and especially for a performance car. I don't know why everyone is thinking less of the car because if you race it, the warranty will be voided. It's basically left to the discretion of the dealership, anyways. And that's assuming something does break, which no one really knows anyways with a new car.
Show me an example of a GT-R owner who's warranty has actually be voided, and then I'll give credit to this. Otherwise, it's just legal bullshit in the owner's manual. I know for a fact you'll find the same stuff in the Viper ACR owner's manual:
"Racing Not Covered:
The warranty does not cover the cost of
repairing damage or conditions caused
by racing, nor does it cover the repair for
any defects that are found as the result
of participating in a racing event. The
term racing includes but is not exclusive
to: wheel to wheel competition, timed
competitive events, autocross or other
off-road track events."
Go here to read:
http://www.dodge.com/en/owners/manuals/index.html?year=2008&nameplate=Viper