Ask HN: What markets are small right now but will be big in 5 years?

Attention (as an actual, formal market)?

Self-driving car rental? (The self-driving matters - it can drive itself to your door. Today, if my car dies and I need a rental, I have to get myself to the rental car place, which is hard since my car doesn't work. And yes, I know that Enterprise delivers, but that takes two people and two cars. That's expensive. A self-driving car would be cheaper.)

Concerts? (I don't mean concert tickets. I mean a market where fans in different cities bid against each other for their favorite acts to come to their town.)