All my BYONDimes to someone who can explain to me why the average person needs a car that goes 200 MPH, or for that matter, why such cars are mass-made and sold.
For the same reason that planes can fly as fast as they do - because they can! Try telling the captain of your next flight that his 757 will get better gas mileage cruising at 175mph instead of 500mph... no matter that it will take a lot longer to get you your destination!
Joking aside - While 200mph is a bit extreme, 200kmh (~125mph) is perfectly fine with me. Distances on the German autobahn are great enough that high-speed travel is a must in many situations - and the newer autos have better engine designs that are actually more fuel efficient around 180-200kmh, and burn cleaner than those who plod along at slower speeds (80-100kmh).
And to knock down an urban myth - you cannot just go any speed on the German highway system. Inside city limits its usually 80-100kmh (50-60mph), and out on the open road then generally accepted rule (that is occasionally enforced by camera systems that do a dang good job of getting your face and license-plate number) is 120-130kmh (75-80mph) as a max safe speed. If you go above 160kmh (~100mph) you start getting noticed by police helicopters and bridge-mounted camera systems... but people usually know where these speed traps are.
Regarding the camera system mentioned above, this ought to be put in use in the States - when I was travelling from Hamburg back to Oldenburg with a colleague in his VW Passat, we saw a brief flash of light ahead of us on a bridge - 2 days later he received a letter with a nice copy of a speeding ticket (180 in a 120 zone), complete with a photo record of his face (from inside the car) and his license plate. Detailed enough that you could tell it was him. He lost his license for 4 weeks... that was a 'First Offense'. This technology would do wonders in the U.S. I think... They also do not rely on radar for speed detection, but instead have sensors just below the road surface that computes your speed between 2 points - almost impossible to fool since you don't know exactly where those sensors are (and they are only a few meters apart, so you can't spoof them by de-celerating quickly).
In Germany it turns out that the lateset BMWs and the high-end Volkswagens actually improve fuel efficiency and reduce emissions at higher speeds - the fuel is burned better in these newer engine designs... so that argument itself doesn't work over here. I remember a story from a colleague who had his new Saab transported to the U.S. laste year. The Customs Inspectors dealing with such things almost did not let the car in because it did not have a catalytic convertor or similar device. The owner actually had to take it to a shop to show that it produced less emissions than the same American imported model! I smell a conspiracy there somewhere... =)