Imagine the possibilities!

Worldwide spending on internet advertising will total $65.2 billion in 2008 — nearly 10 percent of ad spend across all media — and grow 15-20 percent a year to $106.6 billion in 2011 (13.6 percent of total ad spend) according to IDC's Digital Marketplace Model and Forecast, writes MarketingCharts.

The United States will lead the world in both total advertising spend and online ad spend throughout the forecast period, with expenditures in 2011 of over $265 billion and $45 billion respectively, IDC projects (via BtoB).

"By the end of the forecast period, spending for internet advertising will trail direct mail — the third-largest form of advertising — by more than $30 billion, while spend on TV and print ads will each be nearly twice as great as for online ads," said John Gantz, chief research officer at IDC.

Nevertheless, the long-term opportunity for internet advertising is evident in terms of per capita spending, he said: "Total advertising revenues equate to more than $105 per inhabitant of the planet, while internet advertising revenues are less than $50 per active internet user."

MarketingCharts has more findings from the study.