I've had the displeasure of going through AirBnb dispute resolution process more than once, which was resolved in my favour once and not the other. Neither time did I think they did a good job of hearing the sides of the case and deciding on solid principles or written foundations. It's pretty much a matter of who sees it and makes a subjective call. It's also shocking that the first several tiers of customer support is seemingly run by volunteers (or otherwise ill-equipped people).

The success of the trust and brand issue is largely due to the number of well meaning hosts far outnumbering the bad and AirBnb keeping the bad stories not get viral too often.

The 'keep your rating high' has been around since eBay and could easily be copied. I wouldn't have a problem using a service that competed with AirBnb. What they have is a volume lead. People look there because that's where the listings are. Hosts list there because that's where people look.