Sure, airbnb has a $1b valuation for now. But does anybody really think they're worth $1b after this, and only on an estimated $10M cumulative revenue? (not to mention the pending stock market collapse and IPO window closing, precipitated by US default next Tuesday)
They have a pretty toxic public image now amongst early adopters, and will only get worse. They have a business process which now appears to be broken, and it will cut into their already miniscule revenue to fix it. They do not have a moral/charismatic leader that can guide them thorough an important crisis like this. They are deemed illegal in many parts of US, and will likely be more so later once more mainstream media picks up on it.
On top of that, they are destroying yc's precarious image. And they're dragging this entire mess on all the other yc's startups (the other yc founders have to stand up to defend airbnb. Other applicants realizes that the best performing company in yc is one that does evil)