Another story, also well worn, concerns his [Carl Icahn's] taking over ACF, which had operations in the Midwest and a headquarters staff of 173 in New York. He couldn't figure out what they were doing in New York, so he went to the guys in the Midwest and asked them, How many of these guys in New York do you need to support you? And they said, None -- we'd do better without them. But, not to be too hasty, Icahn called in a consultant to analyze the New York operation. Six weeks later the consultant returned with a big black book of charts. Icahn said, Don't give me that, just tell me, what do these guys do? And the guy looked at him and he looked at the guy. And then Icahn took out a check and said, Here -- I'm paying you no matter what you tell me. Now tell me, what the hell do they do? At which point the consultant said, Mr. Icahn, you've been straight with me, so I'm going to be straight with you. We can't figure out what they do, either. So Icahn closed the New York office.
-- from A Predator's Ball, page 190 (search log for Amazon link).

In The Effect of Advertising and Display, there's a study of how people decide what to buy on page 32. This is the breakdown for consumer ISPs:

RecommendationPersonal SearchAdvertising/MediaOther

I wrote Prof. Robert East of Kingston University, the author of the study, for his methodology, to see if it was sane. If it is, then this would tell us how to allocate our marketing budget efficiently. He wrote back promptly, with a sample questionnaire, and paper sample. Unfortunately, he didn't develop the study in which I was interested, but no matter, he's still a good guy.