alt Hacker NewsPrediction markets are not considered gambling for the same reason that stock markets aren't. There's no fixed odds or random chance. A skilled analyst can make consistent returns.
Unlike stock markets, prediction markets also provide valuable data on important world events, such as elections. It's wisdom of the crowd with financial incentive.
Equities markets allow society to collective allocate labor resources and they incentivize the public discovery of business intelligence. Prediction markets reward the public discovery of gossip. Any kind of trading can be gambling depending on how you do it. But with equities the odds are usually almost guaranteed to be in your favor if you long them and wait. I can't remember ever seeing a prediction market where I felt I could have a thesis on its outcome, unless I was spying on people. So I really don't see how they could be anything but gambling for most people.