from http://en.wikipedia.org/wiki/Arbitrage "In economics, arbitrage is the practice of taking advantage of a state of imbalance between two or more markets: ... If you can buy items at one price at a factory outlet and sell them for a higher price on an internet auction website such as eBay, you can capitalize upon the imbalance between those two markets for those items.
One example of arbitrage involves the New York Stock Exchange and the Chicago Mercantile Exchange. When the price of a stock on the NYSE and its corresponding futures contract on the CME are out of sync, one can buy the less expensive one and sell the more expensive. Because the differences between the prices are likely to be small (and not to last very long), this can only be done profitably with computers examining a large number of prices and automatically exercising a trade when the prices are far enough out of balance. The activity of other arbitrageurs can make this risky. Those with the fastest computers and the smartest mathematicians take advantage of series of small differentials that would not be profitable if taken individually."
interesting stuff. if you look at any system close enough, you see its quirks and holes.
the extra links in the text were preserved when copying from firefox into deepest sender.