The New York Times > Technology > Advertising: The Internet Ad You Are About to See Has Already Read Your E-Mail "But the service turns out to have some interesting self-imposed constraints. Google has created what is the electronic equivalent of a television network's standards and practices department to determine which e-mail messages are suitable for ads and which are not.
Google will not display ads on e-mail messages with words related to sex, guns, drugs and other topics it considers off limits. "We want the ads to be family friendly," said Susan Wojcicki, Google's director of product management. "There are some topics for ads we have decided that are not appropriate to be shown on e-mail."