U.S. spending on online and mobile advertising increased to $29.9 billion in 2007, according to PQ Media's "Alternative Media Forecast: 2008-2012" report.

The firm said 18 digital and non-traditional media segments, accounted for 16.1 percent of total advertising and marketing spending in 2007, up from 7.9 percent in 2002.

"By 2012, we anticipate one out of every four dollars spent on advertising and marketing will be earmarked for alternative media," said Patrick Quinn, President and CEO of PQ Media. "Alternative advertising and marketing media are driving a new media order that presents vast opportunities for industry stakeholders, but also key challenges for some of the fastest-growing digital media segments."

Estimates of total US online ad spending in 2007 range from $10.9 billion (Universal McCann) to $30.5 (Veronis Suhler Stevenson).

eMarketer tracks U.S. online ad spending estimates from 23 companies and estimates that online spending was $21.1 billion in 2007.

"Technological advances have led to critical changes in consumer behaviors and media usage patterns, which have pushed the advertising and marketing ecosystems into a seminal period of transition", added Quinn.

"Driven by these market forces, brand marketers are seeking new strategies to connect with consumers through engaging means in captive locations, while at the same time providing proof-of-performance metrics. This confluence of trends is fueling the migration of dollars to alternative media."