As for the users of the Google search engine, we also participated in an exchange of real value, receiving free search services, navigation, office applications, and much more, in exchange for clicking on some of the advertisements that those paying Google customers placed via the service.
What Paul Graham Is Missing About Inequality
Tim O'Reilly

The value of the services Google has given me is far greater than the value I’ve given them through viewing and clicking ads and allowing them the use of some of my data. They can do this because the marginal cost of their product is practically zero. Internet companies that don’t take advantage of this to provide more value to customers are being selfish.