Who gets how many shares when an IPO is oversubscribed?
A broker will only get so many shares for any IPO. They will give their highest profit customers priority, but try to keep the smaller ones happy as well. So where my TWTR order today was for 1000 shares, I actually was granted 100.  In the dotcon* bubble of the late 90's, there were some stocks I saw as many as 1000 hit my account.  (*not a typo, this is the title of a book on that period, the making of a bubble and irrational doings on Wall Street.
Investment banks don't have to buy anything. If they don't think the stock is worth buying - they won't. If they think it is - others on the secondary market will probably think so too. Initial public offering is offering to the public - i.e.: theoretically anyone can participate and purchase stocks. The major investment firms are not buying the stocks for themselves - but for their clients who are participating in this IPO. I, for example, receive email notifications from my brokerage firm each time there's another IPO that they have access to, and I can ask the brokerage to buy stocks from the IPO on my behalf. When that happens - they don't buy the stocks themselves and then sell to me. No, what happens is that I buy a stock, through them, and they charge me a commission for the service. Usually IPO participation commissions are higher than regular trading commissions. Most of the time those who purchase stocks at IPO are institutional investors - i.e.: mutual funds, pension plans, investment banks for their managed accounts, etc. Retail investors would probably not participate in the IPO because of the costs, limited access (not all the brokerage firms have access to all the IPOs), and the uncertainty, and rather purchase the stocks later on a secondary market. Let's clarify some things. Companies allow for the public to purchase their shares through Initial Public Offering (IPO) (first-time) and Seasoned Public Offering (SPO) (all other times). They choose however many shares they want to issue depending on the amount of capital they want to raise. What this means is that the current owners give up some ownership % in exchange for cash (usually). In the course of IPOs and SPOs, it can happen that the public will not buy all shares if there is very little interest, but I would assume that the more probable scenario if very little interest is present is that the shares' value would take a big drop on their issuance date from the proposed IPO/SPO price. After those shares are bought by the public, they are traded on Exchanges which are a secondary and (mostly) do not affect the underlying company. The shares are exchanged from John Doe to Jane Doe as John Doe believes the market value for those shares will take a direction that Jane Doe believes in the opposite. Generally speaking, markets will find an equilibrium price where you can reasonably easily buy-sell securities as the price is not too far from what most participants in the market believe it should be. In cases where all participants agree on the direction (most often in case of a crash) it can be hard to find a party to make a trade with. Say a company just announced negative news with long-lasting effects on the business there will be a surge in sell orders with very few buyers. If you are willing to buy, you will likely very easily find a trading partner but if you are trying to sell instead then you will have to compete for the lowest price against all other sellers. All that to say that in such cases, while shares are technically sellable / purchasable, the end result can be that no shares are purchasable. Only on an accounting basis. The moment they start selling, it would plunge. Take a look at all the small float tech IPOs. Big pop, but once the lockup period ends, it drops 50% as insiders sell. In the end, fundamentals will rule. Facebook managed to unload a quarter of the company at the vastly inflated $38, which is very impressive. The other tech IPOs typically sell less than 10%, because selling more would lead to very low share prices. Remember, these guys are not retail investors selling 100 shares. The ticker shows the price of the last block of shares that was traded, but when someone tries to sell a couple million shares, then it will plunge. Any retail equity brokerage will give you access to the NYSE, and thus Facebook shares as they become available.  However, it is important to note that you nor any retail investor will be able to purchase FB at the IPO prices ($33-38 IIRC).  The only people who will be able to buy in at that price are the underwriting investment banks and major investors who have subscribed to the IPO.  You, and all the other retail investors will only be able to buy in as those major investors offer shares on the secondary market.   This being Facebook, there will probably be a significant premium over the IPO price, both due to demand and systemic underpricing of IPOs to encourage the opening 'pop'.   So, if you're intent on buying in at the IPO, pay close attention as the date approaches.  Look at how the recent big IPOs have performed (GRPN, LNKD come to mind).  Know how much you're willing to commit and what price you want.  However, no one is going to know what the opening market price will be come Friday morning.  Be watching your financial data source / analysis of choice and be prepared to make a judgement. "they are entirely free to do whatever they want with the shares. In particular, they can sell them to whomever they choose No. Restrictions on who can sell when and to whom are a common thing with startups. ""Publicly traded"" companies are regulated in a much stricter way than private companies, so until the IPO the sales are limited to the OTC markets. But even that can be restricted by bylaws - for example ownership can only be limited to a group of investors approved by the board. As an employee - your grant was approved by the board, but when you come to sell, the buyer was not and the company may not agree to vet them. Bottom line is that it is not illegal to impose all kinds of restrictions on what the employees can do with their shares, as long as the shares are not listed on a public stock exchange (even after the company goes IPO with one class, other classes may remain restricted)." "Q: A: Everyone that is short is paying interest to the owners of the shares that the short seller borrowed. Although this quells your conundrum, this is also unrelated to the term. Interest in this context is just the number. In the options market, each contract also has an open interest, which tells you how many of that contract is being held. For your sake, think of it as ""how many are interested"", but really its just a completely different context." Thanks chrissundberg for providing the outline of the JOBS Act. Under the current rules, my understanding is that a non-public company can have up to 35 unaccredited investors, which doesn't really work within a crowdfunding environment. Am I correct in that? To answer your question in its entirety there's more information we need (exchange, session, traded security, order type, etc.). Most exchanges support partial fills, that is your order will be partially executed and modified.  In your example, you'd get an execution of 10 shares at $100, and your order ticket will be modified to $100 for 990 shares. Like John Bensin explained, there are ways to prevent partial filling through order modifiers (e.g. Fill-or-Kill). My addition here is, there are also ways to prevent the other bit, i.e. do the partial fill but don't keep a modified order in the system.  You'd have to mark the order Immediate-or-Cancel (IoC).  In your case you'd be partially filled (10 @$100) and that's it.  For the remaining 990 shares you'd have to enter a new order.