Agreed, my reply was about people canceling to get a "better offer". :) Other than the glitch he mentioned, I think that part of the system actually does work pretty well. Always room to improve though.
That's not the way Airbnb works. You can't cancel someone's booking on Airbnb for a "better offer" from another Airbnb user. If you cancel a guest's booking on Airbnb, Airbnb will block out your calendar for those dates and not allow you to relist your space to rent to another guest - for that time period. If the host HAD double booked on accident through another vacation rental site (Homeaway, VRBO etc), that is the only way they could be canceling to "get a better offer".
On the flip side, as an Airbnb host myself, I have had to cancel a guest's reservation before. It was because of reasons beyond my control (ie. being sent a warning fine from my HOA). Losing the 3% isn't the only thing that happens. #1. You also get a "review" on your listing and profile that says "Host canceled booking X days before arrival". #2. Airbnb drops your listing ranking, meaning you won't show up as high in searches.
Frankly, it's a bad experience for the host and guest, which is why I'm not convinced it happens all that often with hosts who have more than zero reviews. If you book a place with zero reviews, I think it's MUCH more likely to happen, as newer hosts are probably less likely to understand how Airbnb works.