Marketplaces make money by reducing transactions costs / friction and then monetizing a portion of it

The main problems for a marketplace to solve are finding matches, making matches, and learning from matches to make better ones in the future

You generally don’t start by building a marketplace. You start by scaling one side and then you can decide if you want to create a marketplace and scale the other side or just continue to scale that same side.

Not all marketplaces need the same level of data science. Some marketplaces like Uber set prices. Others like Airbnb the sellers set their own prices.

Many experiments in a marketplace have winners and losers. There are rarely changes that are best for everyone. The question is whether the benefit to winners outweigh the losses to the losers.