GUESTS WITH NO PROFILE DESCRIPTION or PICTURE should not be able to book. Simple. Easily implemented by programming. i.e. asterisk'd boxes that don't allow progress to booking if not completed.
If hosts didn't have pictures or descriptions, we wouldn't get bookings.
It sounds like, from the last live Host Q&A segment, that some sort of Super Guest status is coming hopefully along with superguest status, average requirements for filling out information will be included. Airbnb was not made successful by anonymous, generic hotels and motels, but of people across the world opening their _homes_.