Options and futures often carry higher commissions than equity trades and investors in futures will be required to maintain a minimum margin.

FORBES: Profiting From Fear With Exchange-Traded VIX Notes

The bottom dropped out for the fast-growing brand a darling of the investment community, retailers and consumers with a second-quarter report released in August where the company changed its outlook from expecting a revenue growth of no less than 30 percent for 2011 and an EBITDA margin of minimum 40 percent with flat revenue and EBITDA margins in the low thirties for the year.

FORBES: Pandora Revenue Flat for 2011

They have to commit to a minimum trading volume, and a maximum margin between bid- and offer- prices.

ECONOMIST: South Korea

If Mr. Market trashes your investments in a sudden panic, your margin debts may be "called, " forcing you to sell some of your assets to sustain the minimum account values you committed to under the terms of the loan.

WSJ: The Intelligent Investor: Borrowing Against Yourself