Its also ripe for abuse; create dummy accounts that use their free stays to give a host credit, then the host sells those credits for real money.
On a certain movie tracker some invite selling scum would join via the signup process that used to exist on reddit, cheat a bunch of upload on popular torrents, convert that upload into bonus points, launder the points to their main account through a forum contest where they also gave away BP to innocent users, and buy invites to sell for real $ with the laundered BP. Similarly the dummy camping accounts could make sure to mix in some legit hosts as their free stays by picking hosts that may not be around/able to verify the dummy account stayed at their location (because it didn't).