Clickz: Contextual Advertising in Context, Part 1

Good analysis of Google's move into contextual advertising.

Google's strength is it already knows about the vast majority of important pages on the Web. The company has indexed well over 2 billion pages (the 3 billion figure on its page includes some pages it's never visited but knows about via link analysis). This means, according to Google, it can easily deliver targeted ads to any page participating in its program.

Google says just by inserting a small amount of code publishers who enter the program can get the company's targeted ads. The potential exists for the entire Web to be Google's ad canvas. Everything online could, theoretically, become Google's indirect content.