I'm not really sure about this customer/product distinction. Both the people who view the ads and the people who buy the ad placement give Google something they

I'm not really sure about this customer/product distinction. Both the people who view the ads and the people who buy the ad placement give Google something they want in exchange for something they have. That is, Google has products and services that it gives to customers in exchange for their eyeballs. Then, Google is able to convert some of those eyeballs into clicks, which they sell to advertisers in exchange for money. The transfer of goods in exchange for value is not only possible when money exchanges hands. If Google was unable to create products that convinced one of its classes of customers to sell their eyeballs, they would not be able to resell the eyeballs for cash.