Positives:

  1. You need money to participate even though your position size may not matter if really small based on liquidity and volume.
  2. Useful information if looking at overall sentiments especially traders
  3. Noise filter because its not same as trolling on social media
  4. Opportunity for some people to make money
  5. Entertainment and something new to discuss or confirm bias

Negatives:

  1. You need money to participate. "Full nodes enforce consensus rules" becomes a meme. Full nodes will still enforce consensus rules but some full nodes are being influenced by people with money which can be anything not necessarily bitcoin.
  2. Information that may not be useful for everyone.
  3. The exchanges who have created such markets in past and the traders involved know how to manipulate illiquid markets at least for a short time period. And sometimes "markets can remain irrational longer than you can remain solvent". 
  4. If such markets affect Bitcoin development in any way, it will be great opportunity for governments to attack Bitcoin. Example: Consider we have a soft fork or hard fork for confidential transaction on-chain in future, if someone is able to find a secure way to implement it. All the governments that love to spy will have some issues with it and won't be the first time if they participate in such markets indirectly to manipulate or start some investigation against exchanges involved or something else.
  5. Focus which should have been on improving Bitcoin will now shift to futures markets and their involvement in Bitcoin.

I think prediction markets or such tokens might help in adding to the information we already have however they don't decide or replace anything. Bitcoin development should impact such markets and not the other way around.  Nobody can stop markets from betting on something related to Bitcoin and it can even be done using P2P exchanges like HodlHodl: https://predictions.hodlhodl.com or create something new with oracles which can be implemented using DLC: https://github.com/discreetlogcontracts/dlcspecs 

Not everyone is a trader or interested to take risk in such markets even if a Bitcoin user from years, lot of transactions, contributions and some opinion on Taproot based on things that are publicly available to everyone but scattered. In past we had things that made some sense for prediction markets like 2x and Bcash but right now nobody has issues with Taproot and even the best traders won't be aware of all the technical details about Bitcoin development to predict something related to activation mechanism. 

If the point of using prediction markets is to filter noise or spam then maybe we can have one chatroom that requires some sats to enter and pay some sats for each post. We will have better information here and sats can be used to donate to devs who review PRs related to Taproot. 

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Prayank