In this case, they are ranked by how many ads each bought in prime time shows PTC gives a green light for family oriented (best), and ones they give are red light for sexually graphic, violent and profane (worst) content they say is inappropriate for kids.
For example, advertisers with heavy commercial loads in red-lighted shows like Desperate Housewives, Grey's Anatomy, Two and a Half Men, According to Jim, CSI, Charmed, Medium, and Law & Order are deemed the "worst."
The best advertisers are those in shows on the almost-unseen Pax Network and ABC's Extreme Makeover: Home Edition, the only Big Four network show PTC gives its green light for family friendly (American Idol is another, but it is not currently on the schedule) with that caveat, the "best" are Coke, Campbell Soup, Walt Disney Co., Ford, Cingular, Altria (Kraft, Post, and a supermarketful of other name brands), DreamWorks, Schering-Plough, Darden Restaurants (Olive Garden, Red Lobster, etc.), and Sears.
The "worst," committing the offense of advertising in most of the most-watched shows on TV: GM, Toyota, Volkswagen, DaimlerChrysler, Target, GlaxoSmithKline, Nissan, American Express, Apple, and Circuit City.