Economist.com | Internet advertising: "This year the combined advertising revenues of Google and Yahoo! will rival the combined prime-time ad revenues of America's three big television networks, ABC, CBS and NBC, predicts Advertising Age. It will, says the trade magazine, represent a 'watershed moment' in the evolution of the internet as an advertising medium. A 30-second prime-time TV ad was once considered the most effective form of advertising. But that was before the internet got going. This week, online advertising made another leap forward.
This latest innovation comes from Google, which has begun testing a new auction-based service for the more sophisticated advertising of brands, rather than of just individual products. Both Google and Yahoo! make most of their money from advertising. Auctioning keyword search-terms, which deliver, along with their own search results, sponsored links to advertisers' websites, has proved to be very lucrative. Advertisers like these links because, unlike with TV ads, they pay only for directly measurable results. They are charged when someone clicks through to their own website."
(Subscription required for full article; I guess economist.com can't support itself on advertising revenues yet...)