Do you really think the Airbnb guys haven't considered this possibility?

People who do that sort of thing leave lots of tracks they don't realize they're leaving.

Like? If I emailed a few friends around the country and asked them to help me out like that, how would Airbnb know?

I'm not saying they haven't considered it, I'm saying they can't stop it. Making the claim that a transaction based review system is inherently trustworthy seems either naive or disingenuous.

And if they have considered it, what are they doing about it? I'll bet you a thousand dollars if the suggested scenario happens, there is no mechanism in place to alert anyone, stop it, or deal with it, no matter how big the tracks left. Do you know how many of the NYC listings are pure scam?

I'll grant their review system is set up from the get-go to be the best of anyone out there.

When I was in Vietnam last year I booked a few cheap hotels in the 10-20 U$ a night range (nice ones by the way!) on Agoda.com. Often the reviews went like "best breakfast in Asia" or "I will come back to Vietnam just to stay in this Hotel" but when I went there, they where nice but not THAT nice. Once I went here http://www.agoda.com/asia/vietnam/hoi_an/sunflower_hotel.htm... as the reviews where incredibly good: but as I found out the internet was very slow, breakfast was a deception, the reception a bit rude and they even gave me a smaller room. So I wrote a review adding to be careful about fake reviews. Sure enough Agoda did not publish it and they did not even respond to my email asking why. I did not expect a Facebook debit card but at least a "thank you" :) After all I helped them spotting cheaters! I was completely ignored.

The result is a side flooded by fake reviews costing a couple of bucks each to the Hotel manager. That's cheaper than Adwords :)