An analysis by Fortune:
Google’s most successful search advertisers are those who methodically experiment with multiple messages. Sometimes they try thousands of combinations of different texts displayed in response to various search keywords, quickly – often in hours – eliminating those that don’t attract the clicks of users and refining those that do, until they arrive at the ideal combination of message and keyword.
A similar process of refinement takes place in Google’s AdSense service. It places ads on the Web sites of affiliates with which it shares ad revenues.
I don’t know if they’re right, but Google’s managers now seem to believe they can do the same thing with print, radio and TV, albeit with much of the testing taking place on the more immediate and low-cost medium of the Internet. Buying YouTube will give Google a platform on which advertisers can experiment with TV ads in different forms.