Cadillac has been widely, and incorrectly, reported as paying for a product placement campaign in Mad Men. Actually, Cadillac has not paid for its role in the series, and a spokesman said AMC did not even contact the carmaker before it appeared in the show.
During season two, Don Draper buys a 1962 Cadillac Coupe deVille at his boss's urging. That episode ends with Betty, Draper's wife, vomiting in the car's deluxe interior. Show creator Matt Weiner has publicly stated in the past that a car company would not willingly pay for that kind of image -- and in this case he is probably right.