I have been an airbnb host for 2.5 years and am a super host. I am horrified by this idea of being forced to use instant book.
Several problems not mentioned:
1. Sometime we need to communicate with the guest to make sure it is a good fit. With instant book, that is not possible until after the fact. This then costs a lot of time and trouble. It can result in poor guest service.
2. This turns the situation into a hotel--where anybody can book. When I have used Instant Book, I have had a few guests who thought this meant it should be like a hotel--check in whenever, do whatever. One couple actually said they did not want to see me in my home because it was instant book. They did not like it that they were greeted in the shared kitchen in the morning. This was a one night honeymoon kind of trip.
3. Sometimes people are in a hurry and instant book without reading the listing. Obviously, problems can arise when that happens.
4. Advocating for airbnb: I am a strong advocate. I have praised airbnb as a wonderful option that brings people together. I have explained that it is not like a hotel, and that guests are screened carefully (no stranger danger). I cannot honestly say that anymore if any host anywhere is forced to use instant book.