Day speaks from experience in this column, having been involved in having Sex and the City star stand alongside Daimler CEO Dieter Zetsche at the Detroit Auto Show a few years ago along with other other stunts. 

To me seeing cars and celebs in these environments does more to turn me away rather than toward the car. Audi has long been particularly egregious in this regard although many companies have been guilty. 

If celebs buy the cars with their own dollars, promote it. If you have to pay them to sit in your car forget it. ?