Did you know that Google has "a trademark policy, which prevents bids on other people's registered trademarks, and we do not allow people to advertise with AdWords for counterfeit products."

The basic issue is whether a competitor can buy a trademarked term as a keyword -- so that someone looking for "Ford" is taken to the General Motors website, for example. Trademark owners, being a touchy lot, think the practice clicks on "infringement," so Google has good reason to avoid the problem.