From http://www.sipc.org/

    SIPC is the first line of defense in the event a brokerage firm fails owing customers cash and securities that are missing from customer accounts. Although not every investor is protected by SIPC, no fewer than 99 percent of persons who are eligible get their investments back from SIPC. From its creation by Congress in 1970 through December 2006, SIPC advanced $505 million in order to make possible the recovery of $15.7 billion in assets for an estimated 626,000 investors.

    When a brokerage is closed due to bankruptcy or other financial difficulties and customer assets are missing, SIPC steps in as quickly as possible and, within certain limits, works to return customers’ cash, stock and other securities. Without SIPC, investors at financially troubled brokerage firms might lose their securities or money forever…or wait for years while their assets are tied up in court. However, because not everyone, and not every loss, is protected by SIPC, you are urged to read this whole brochure carefully to learn about the limits of protection.

    SIPC is not the FDIC. The Securities Investor Protection Corporation does not offer to investors the same blanket protection that the Federal Deposit Insurance Corporation provides to bank depositors.

    How are SIPC and the FDIC different? When a member bank fails, the FDIC insures all depositors at that institution against loss up to a certain dollar limit. The FDIC’s no-questions-asked approach makes sense because the banking world is “risk averse.” Most savers put their money in FDIC-insured bank accounts because they can’t afford to lose their money.

    That is precisely the opposite of how investors behave in the stock market, in which rewards are only possible with risk. Most market losses are a normal part of the ups and downs of the risk-oriented world of investing. That is why SIPC does not bail out investors when the value of their stocks, bonds and other investments falls for any reason. Instead, SIPC replaces missing stocks and other securities where it is possible to do so ... even when the investments have increased in value.

    SIPC does not cover individuals who are sold worthless stocks and other securities. SIPC helps individuals whose money, stocks and other securities are stolen by a broker or put at risk when a brokerage fails for other reasons.

    Investments protected by SIPC. The cash and securities – such as stocks and bonds – held by a customer at a financially troubled brokerage firm are protected by SIPC. Among the investments that are ineligible for SIPC protection are commodity futures contracts and currency, as well investment contracts (such as limited partnerships) that are not registered with the U.S. Securities and Exchange Commission under the Securities Act of 1933.

    Terms of SIPC help. Customers of a failed brokerage firm get back all securities (such as stocks and bonds) that already are registered in their name or are in the process of being registered. After this first step, the firm’s remaining customer assets are then divided on a pro rata basis with funds shared in proportion to the size of claims. If sufficient funds are not available in the firm’s customer accounts to satisfy claims within these limits, the reserve funds of SIPC are used to supplement the distribution, up to a ceiling of $500,000 per customer, including a maximum of $100,000 for cash claims. Additional funds may be available to satisfy the remainder of customer claims after the cost of liquidating the brokerage firm is taken into account.

    The Securities Investor Protection Corporation was not chartered by Congress to combat fraud.
    "Insurance" for investment fraud does not exist in the U.S. The Federal Trade Commission, Federal Bureau of Investigation, state securities regulators and other experts have estimated that investment fraud in the U.S. ranges from $10-$40 billion a year. In the case of microcap stock fraud, the toll on investors has been estimated as $1-3 billion annually.
    With a reserve of slightly more than $1 billion, SIPC could not keep its doors open for long if its purpose was to compensate all victims in the event of loss due to investment fraud.