Earlier quoted context omitted.
The idea is that people have all sorts of fragmentary information about future events that they can't directly reveal, due to confidentiality or trade obligations (among other things), and that a prediction market effectively liberates the directional content of that information by converting it into prices. Robin Hanson can credibly claim to have invented prediction markets as we understand them today.
"that a prediction market effectively liberates the directional content of that information by converting it into prices." I can see this, and I guess maybe my issue is with the phrasing of "aggregating" insider information. Because you aren't just aggregating insider info, you are also aggregating non-insider information, but no one (but the insider) knows what is right. Is there different types of prediction market…
What's the difference between a "Monday it will rain" market and a NCAAF prop bet on a team's rushing yards? I could argue that DraftKings prop bets are actually more like prediction markets than these "will it rain" bets. People actually do have directional information to contribute to sports propositions!
(I think online sports betting is evil.)