Emergence of digital media greatly changing the advertising world

New companies dominate technology-driven world of making, delivering Web ads

Marketers have steadily moved more of their ad dollars online

Traditional agencies and Silicon Valley giants now battling for more of digital ad dollars

Online advertisers can be more scientific about where their ads are placed due to behavioral targeting

Internet advertising was $16.9B industry last year, representing 5% of $285B spent on ads in US

Google recently acquired DoubleClick, Microsoft bought aQuantive, and WPP bought 24/7 Real Media

Much of attraction to online advertising based on its precision

Online, ad networks buy up space from Web sites and resell to advertisers

While ad-serving firms deliver ads from advertisers to sites where space has been purchased

"The biggest innovation in the advertising industry during the last 70 years before digital was color TV. The agency of the future will be half a software company and half an entertainment company because that's the new landscape." -- Ajaz Ahmed, chairman and co-Founder, AKQA

"Ad serving is kind of like oxygen. You need it for every major [online advertising campaign] that you run." -- Sarah Fay, president, Aegis Group PLC's digital-marketing subsidiary, Isobar U.S.