So the value changes over time. Nothing to be surpised at. If everyone knew how a company was going to do, the stock market wouldn't be necessary, and they'd be traded like bonds. Actually, the owner would probably issue bonds instead of giving up a controlling position, but that's a technicality.

For a growth stock, the question is always when the growth is going to stop. Is google going to once again some day be the company that just provides a lone search box on their home page? Or are they going to provide you The Google Desktop and leave you with no need for a windows computer? The search box and associated advertising are decent money makers, but it's the all encompassing google desktop or hope of some other revolutionary product that really props up thier stock price. If it becomes increasingly clear that WYSIWYG with google, the stock price will come down to match their earnings much more closely.

Matthew