A Letter from Larry PageGoogle Search has to work so that Google's advertising revenue grows. When content is missing, Google does not build the solution (can't scale), they build the ecosystem.
...Sometimes you don't get a good answer to a search because the information simply isn't available on the web. So we are working hard to encourage ecosystems that can generate more content from more authors and creators....
Blogger is one obvious example. I'm still amazed by how often what I write in my tech blog appears at the top of Google searches -- despite a very small subscription readership. I write things that fill content gaps, and Google finds them.
Google Books is a less obvious example that might yet have a big influence. On the other hand, Google gave up on Google Answers -- a ecosystem that failed.
I wonder how far Google will go to provide an ecosystem for content producers, and to open new knowledge fronts. They have very large levers! Google Scholar is being used to increase readership of open journals, and thus weaken the publishing empires that keep vast amounts of knowledge hidden from most of the world. Regular Google Search was used to crack open the New York Times and end their experiment with paid access.
Google could buy the Encyclopedia Britannica, but I suspect they're looking for ways to pressure them to run off Ad Words ...
I wish Google would try micropayments other than through advertising, but that's only a weak wish. So far humans have been really resistant to the idea.