This graph of one trillion URLs is similar to a map made up of one trillion intersections. So multiple times every day, we do the computational equivalent of fully exploring every intersection of every road in the United States. Except it'd be a map about 50,000 times as big as the U.S., with 50,000 times as many roads and intersections.
As you can see, our distributed infrastructure allows applications to efficiently traverse a link graph with many trillions of connections, or quickly sort petabytes of data, just to prepare to answer the most important question: your next Google search.
All this technology has been brought to bear so we can find information about these things.
And it all seems to be funded by little, unobtrusive text ads.