I think that's absurd. Would you say the same thing about Craigslist?
> The fact that they don't know the identity of the parties is openly misrepresented by their materials which indicate that the transaction is safe and intentionally try to distract the customer with jokes about the difficulty of moving grand pianos
That's not how I read it at all. They don't claim to know the identity of the other party; they claim that the transaction is safe. Which, it appears, it is. If they've had 2 million nights booked, that's maybe a quarter of a million bookings, and (they claim) this is the first time anything like this has happened. That's pretty safe!
I read the joke about the grand piano as an admission that the only thing that's preventing people from using Airbnb to rob people is that robbing people is generally hard and unprofitable.