• What are the advantages of Instant Book? Guests usually prefer to book instantly. It saves time and makes it easier for guests to plan the rest of the trip. Instant Book ensures that every guest can receive equal treatment (no discrimination).
• Will you get more bookings if you turn on Instant Book? Yes, most probably. Instant Book listings (e.g. vacation rentals) are ranked higher in search results. Currently more than 60 % of bookings on Airbnb are booked instantly.
• Why is Intant Book default for new hosts? Instant Book will soon be the prefered booking method on Airbnb. Instant Book is aligned with Airbnb’s mission of creating a world, where people can belong anywhere. Guests prefer to book instantly and hosts have the potential to earn more.
• Can I prevent a guest, with whom I had bad experiences in the past, from booking my accomodation in the future via Instant Book? Yes!
• Will I have some control around who stays in my home? Guests must meet certain requirements in order to book a home on Airbnb (e.g. verified phone number, email address, payment information). Furthermore Instant Book guests have to verify their ID since Instant Book hosts don’t have the opportunity to review every guest. Hosts are allowed to limit Instant Book reservations to guest with only positive reviews.
• Why does Airbnb give a search boost to hosts, who have Instant Book turned on? Guest will have a better booking experience and hosts have the potential to earn more money.
• Is it possible to turn off Instant Book? Yes!
• Is it possible to cancel an Instant Book penalty-free (no impact on Superhost eligibility, no fees etc.)? Yes, if a guest breaks a house rule or intends to break a house rule and if a host feels uncomfortable with a reservation. But if your reason violates Airbnb’s Non-Discrimination policy you may not be penalty-free.
• Doesn’t Airbnb take away the personal touch by pushing instant book? It isn’t Airbnb’s goal to take the personal touch away. Airbnb wants to help hosts to spend less time on the logistics of booking (emailing back and forth etc.).
• Will an accomodation disappear from search as soon as Instant Book is turned off? No, but some guests may set a filter for Instant Booking listings. In this case, listings that have Instant Book turned off will not show up.

(Source: via @Airbnb – Get full details at https://blog.atairbnb.com/instant-book-questions/ )