"But how will Google ever make money? There’s the rub. The company’s adamant refusal to use banner or other graphical ads eliminates what is the most lucrative income stream for rival search engines. Although Google does have other revenue sources, such as licensing and text-based advertisements, the privately held company’s business remains limited compared with its competitors’."
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Originally from Business Week in 2000. Re-published on cdixon.org.
An interesting perspective when thinking about places like Facebook and Twitter whose new users experiences and traffic growth may preceed revenue growth as they experiement with different models.