Stock markets are secondary markets. If Google's stock dropped by 3/4 Tuesday afternoon it would have little effect on the company's operations, though it would affect their ability to raise additional money in the future.

Of course Google's executives and other investors would be in personal pain. Look at Red Hat, which dropped from almost $150 to $3 in well under a year and they're still around ($22 on Friday).

But contrast Google to Red Hat. Red hat started at around $45 and was up to almost $150 in a few months, then started the slide to $3. Google started at about $100 and climbed at a modest rate to around $500 and then stabilized in a range between $450 and $500.

Red Hat was a perfect example of an IPO with plenty of hype but no viable business plan to achieve profitability. They spiked very early and dropped fast - until they got their act together and showed some profitibility.

Google's stock price is a good example of an IPO for a company with a real plan, profitability, and the probability of plenty more profit. Don't expect them to drop too far unless the general economy goes to hell.