Yes, Starbucks is everywhere. Even in London Taxi Rush Hour.
Youniversal Branding provides an excellent primer on gamevertising, with stats, tips, examples, and agencies.
The optimum role for a brand within a game is to enhance the gamer's sense of escapism, by strengthening the alternate reality experience.
That's why I call it gamevertising, not advergaming. The game defines the campaign, not vice-versa.
(Via JC Cuneta.)