They could fix the review process by weighing the review by the amount paid for the stay (or some similar formula). So your buddy who "pays" $20 and then writes

They could fix the review process by weighing the review by the amount paid for the stay (or some similar formula). So your buddy who "pays" $20 and then writes a fake review would have their review dwarfed by real users who pay the full price. An interesting question is: is it better to optimize for more inventory or better quality?