To everyone asking "how do i buy this stock at IPO?"- please think long and hard about this. Do you really want to buy on day 1 when the scam underwriters on Wall Street have already sold the stock to their institutional investors at a 10-20% profit? That profit is coming from you, the pig investors who will buy at day 1, see a tiny drop instead of the big bump you expect, and then sell for a loss. If you aren't a seasoned trader, just stay away.
TL;DR- If you have to ask, you probably shouldn't do it.
Would you care to elaborate on how exactly this "scam" works?
The job of the underwriter is to guarantee that a certain amount of stock is sold at the point of IPO. They are paid to canvas their clients and market the IPO. That is what they do. I would strongly recommend you try and understand how IPOs work and how capital is raised before you bring out the pitchforks.
If you are curious, I would recommend reading the blog post below which will explains, probably better than I ever could.
[EDIT]: Let me just add - yes, the underwriters may offer the stock to their clients at a rate that may be lower to where the market goes when the shares start trading. The underwriter's clients may decide to take profit in the first few days if the price shoots up. The stock price will be volatile either way. So if you are considering buying Facebook stock, and are prepared to hold for a while, buying at the time of opening may be OK. If you are afraid of short term volatility, wait until the price settles down.
TL;DR- If you have to ask, you probably shouldn't do it.