Stocks are only worth so much a share depending on the value of the business. When you multiply the stock price by how many shares there are you get the company's Market Cap, which is what you could buy the company for if you could get your hands on all the stock at that price.
This value should closely reflect a mix of the following: What someone would buy the company for if it had a sale sign on the front door, what the company is making in profit and what the company is paying in dividends, plus any sum of money on top for the prospect of all these ingredients going forwards.
Of course that doesn’t necessarily equate to the share price, which is what investors try to make money out of.
Facebook is valued like a superstar. If you took the way Exxon is valued and applied it to Facebook it would be worth a few cents a share. Even if you put it up against Google or Apple you would be hard pressed to see the stock over $10. Facebook was floated at an amazingly high price because its brokers sold the initial investors a dream that Facebook was the most amazing company in history. That dream is tarnishing so its stock price is cratering.
You only have to look at the dotcom boom -1995-2000 - to see how this story goes. But wait, many dotcoms had a rough start and then shot to the moon before collapsing back again. This is not a simple story, which in itself is another reason to steer clear. Never ever invest in a stock story you don’t understand because that’s a game you will always lose.