Bad drivers are indeed a problem on the Autobahn. I grew up close to Denmark and during the holiday seasons they flood the Autobahn because any traveler going south had to come through one choke point. Speeding is very expensive in Denmark and thus nobody would really exceed the limit by much. This means that these fellows might do exactly what LondonElite wrote: pull out of the right or middle lane at 120km/h while you are doing 220+ km/h. The difference is more than what the legal speed limit in most of the US is and drivers need to be aware.
I had to slam the brakes once in a rental car and it pulled towards the barrier - quite scary. I confronted the rental car company upon return and a week later I got a letter 'thanks for letting us know. The wheel-whatever-break-something was broken and we should not have rented the car out.'

Also remember that even a 1 series BMW (unless it's the bare bones model) has enough power to do 220km/h so there's no need to get a ridiculously overpowered car at a high price (and associated risk).