More from the YPulse 2008 National Mashup, a two-day conference on teens and technology in San Francisco: CNET News reports that advertisers clamor to reach teens in digital environments because "that's where they're spending much of their time—either online, with cell phones or playing video games." That's to the tune of an estimated $200 billion annually—not chump change when you're talking about discretionary spending.

"The iPhone is just the beginning of the all-in-one device. Uses of mobile devices will expand to include all kinds of bar code applications and prepaid debit card payment methods," said Bill Carter, a partner at Fuse, who presented his research findings according to the report.

Analyst predictions are that cell phones in the United States will surpass the popularity of desktops for teens. (That's already true in some other countries.) "Only an estimated 20 percent of teens currently own a smartphone such as the iPhone, but mobile phone and content companies are counting on the idea that smartphone adoption will spread fast among teens in middle America and other areas," the report said.