Early ads for the Touareg showed one towing an Airstream. Those ads had to be pulled as it is technically not possible with the Touaregs towing capacities. Those capacities are 7700 lbs with 616 lbs at the tongue. Turns out an Airstream, while under 7700 lbs, apparently puts more than 616lbs at the tongue.
I don't know anything about the Airstreams, but apparently the largest version, which VW showed in the early ads, puts too much weight at the tongue.
Here's a link to a story on the Touareg and the Airstream snafu:
http://cbsnewyork.com/shamestories/local_story_303155456.html
On the other hand, we absolutely love our T-reg.