Mirroring.

It's that simple.

Google has a huge amount of data, spread over many international locations. And there are many people in, say, France, who might want to query data held elsewhere, say, in the U.S.

As Google's translation services grow, this becomes more likely.

Google's telecommunications bills must already be extraordinary, in order to handle this traffic.

If Google had its own dark fiber network, it could light that fiber and drive those costs to the ground.

Then the fiber would be open to other applications, such as:

• Mirroring the entire database in multiple sites.
• Caching the database, or portions of it, where laws are most advantageous for that.
• Caching such things as images.
• Offering a video database.
• Creating "Google libraries" of others' data and mirroring it to the central database.

But if Google is stuck buying capacity from Bell companies and other local monopolies, it can easily be strangled.

No smart business wants to be strangled.

Google is just being Clued-in.