Via David Pennock of Odd Head fame
[…] I believe that online political prediction markets, and other online prediction markets as well, should be legal in the United States and elsewhere, even if the amounts bet were quite large. There is no important substantive difference between such online betting markets and the Chicago Mercantile Exchange and other exchanges that allow individuals and organizations to take positions on movements of stock indexes, housing price indexes, and prices of other derivatives. A distinction is sometimes made between political betting markets and derivative markets since participants in derivative markets may be hedging other risks that they face. Yet this distinction has little substance since if larger bets were allowed in online political markets, groups whose welfare depended greatly on political outcomes would make greater use of these markets. For example, if a Republican presidential win would mean greater spending on military weapons, companies in the arms business might hedge their risks by betting on Barack Obama.
If large bets were allowed, some wealthy groups may bet a lot on their candidates in order to exert bandwagon influences on public opinion through their large bets affecting market odds. If so, these markets likely would become less reliable as predictors of outcomes, and hence would have less influence on opinions. To a large extent, therefore, these markets would be self correcting, although online political markets might place various other restrictions on bets, as is common in derivative and other exchanges.
[…] There is an interesting question whether prediction markets should be thought of as “-gambling” and perhaps prohibited. As a matter of policy, that would be a mistake, even if one thinks that gambling should be prohibited. The prediction markets are markets for speculation, rather than for game-playing or risk-taking. Slot machines, card-playing, roulette wheels, and other conventional forms of gambling do not generate socially valuable information. Speculation does. Commercial speculation serves to hedge commercial risks and bring prices into closer phase with value. Political, cultural, etc. prediction markets also yield socially valuable information. The outcome of elections is important to companies and even individuals for whom particular public policies are important- they may wish to make adjustments to avert or exploit looming political change. Politicians too need to have as sharp a sense as possible about the effects on the electorate of their and their opponents’- strategies. Apparently they can get more accurate information from the prediction markets than from the public opinion pollsters.