In the weekend Daily Telegraph Motoring section today, there's an article about the "Best Tow Cars" ratings for 2011.
They certainly have a different opinion about how much you can tow.
For a trailer up to 3100 pounds, the Ford Focus won. For up to 3500 pounds, the winner was the VW Golf TDI. For up to 4000 pounds, the best was the Ford Mondeo (briefly sold in the US as the Contour or the Mercury Mystique).
At 4200 pounds, the Jaguar XJ diesel was the winner (not sold in the US) and for over 4200 pounds (no upper limit specified), The Land Rover Discovery won.
Highly recommended were the Kia Sportage 2.0 diesel and the Audi Q7 TDi, but weight ratings were not specified.
To see the full article, go to www.2008/jun/practical-caravan-what-car-and-the-camping-and-caravanning-club-name-ford-mondeo-estate-as-britain-s-best-towcar/
The "weight police" on here and on RV.net would have a fit!