AdWeek.com – NEW YORK For Internet ad giants like Google and Yahoo, the Toyota Scion brand should be a dream marketer. With an 18-24-year-old trendsetter target audience, the carmaker sees the Internet as key to its marketing efforts. But while other auto brands buy up keywords and run banners and pre-roll spots online, Scion takes a decidedly alternative route, relying instead on virtual worlds, its own broadband video site and viral gaming to reach an audience averse to ads, offline or online.