Most investors agree that Google Inc. (NASDAQ:GOOG) is a great company. There is less agreement, however, about its stock price. The billion dollar question is whether Google can keep growing fast enough to justify its high price.

At $460 a share, its PE ratio is about 60. This suggests that at the first sign of slowing growth, the stock could easily fall by half. This is definitely not what Google enthusiasts have in mind.

The pessimistic case for Google is made today over at The Motley Fool. Chuck Saletta points out that Google's revenues are about $9.3 billion. This means that a one percent growth in revenue requires an additional $93 million dollars. The advertising market is notoriously turbulent, and can quickly shrink in the event of an economic turndown. So revenue growth for Google is by no means assured. There is also the competition to worry about. Yahoo! Inc. (NASDAQ:YHOO) and Microsoft Corporation (NASDAQ:MSFT) are not sitting on the sidelines watching Google dominate internet search. Both companies are spending millions to claw their way into Google's territory and there's good reason to think that they will have some success -- which means a lower price for Google in 2007.

The optimistic case for Google is harder to nail down. Somehow $2.4 billion in earnings is supposed to justify a market cap of over $140 billion (!). But if any company is worth such a rich valuation, it's Google. There's a great scene in the movie Chinatown where the troubled hero Jake Gittes (Jack Nicholson) asks all-powerful Noah Cross (John Huston) why he tries so hard to control everything around him. Here's the scene:

Jake Gittes: I just want to know what you're worth. Over ten million?
Noah Cross: Oh my, yes.
Jake Gittes: Why are you doing it? How much better can you eat? What can you buy that you can't already afford?
Noah Cross: The future, Mr. Gittes, the future.

I think Google may be our Noah Cross (though hopefully without all the incest and murder). More than any other company, Google is poised to dominate our collective future. What company is better positioned to control an age of pure information? Such power may be hard to price, but it's certainly worth a lot. So maybe $460 a share is a small price to pay for controlling the future -- a future which includes an even higher share price for Google in 2007.