I don't have any reason to believe the market has "priced
    in" the value of Google's future growth

Why don't you think people deciding how much to pay for Google stock are considering Google's expected growth? Google's market cap is similar to Exxon's with far lower revenue and much lower profit.

    Dollar cost average into it, and be a buy-and-hold
    investor, and it's hard to go wrong.

It's not hard at all to go wrong that way: investing in only one stock is unnecessarily risky. If you're picking individual stocks you should be asking "what's my edge?" or "what do I know that other smart informed people don't?" Sure, you see lots of potential for growth at Google; so does everyone else, that's not going to make you any money. Unless you're better informed in a useful way it's much better to just buy a slice of the market with index funds.

Of course the people buying Google stock are considering expected growth. (Though I wouldn't call market dynamics "deciding." You humanized that in an interesting way.). But I don't think all future growth is priced-in to the stock. Nor should it be. The question is, do you think there is upside, can your investment grow as the company grows.

I've always been fascinated by the people who prescribe index funds to everybody as the only right play. Of course I own index funds. Over half my total portfolio is in tax favored retirement accounts and all of that is in low-cost index funds. But if you have more tolerance for risk and a desire to personally manage your money, investing smartly and holding for the long term is a perfectly reasonable and often profitable strategy.

I stand by what I've said. There is no reason for me to believe that long-term value in Google will not be returned to share holders. There is certainly an amount of risk here. But buy-and-hold is a solid strategy IMHO.