Why don't more businesses use prediction markets?

Tyler Cowen
Marginal Revolution, March 2006
http://www.marginalrevolution.com/marginalrevolution/2006/03/why_dont_busine.html

private businesses had not made a breakthrough with the use of idea futures.  It seems natural to let your employees bet on future business conditions, the success of product lines, or broader questions of corporate strategy.  Microsoft and Google and a few other companies have played with the idea, but it does not (yet?) seem to be taking off.  Why not?