Presently, virtually all of our repeat guests book with us directly - thus avoiding the [not insignificant] Airbnb booking fees. This seems to me to be a significant lost revenue opportunity for Airbnb.
Having a significantly discounted booking fee for repeat guests (staying at the same venue), say a 75% discount, would encourage hosts to still have their repeat guests book through the Airbnb site. The advantage to the host is the simplicity of operation, calendar tracking, insurance coverage, etc.
The advantage to Airbnb is an increased revenue stream (25% of something is better than 100% of nothing), maintaining the loyalty of both hosts and guests, etc.
My 2-cents (or Airbnb billions).
David
David Harrison
The Farm on Old North Road
Huntsville, ON Canada