[abruzzi]

IANAL, but I suspect that they want to know as little as possible about specific users. If the play dumb and mention that you may need to check with local laws about the legality, then they can play dumb in court. If they know too much, they become complicit in the "crime" and may be fined, etc.

[frandroid]

They might "want to know" as little as possible, but they know the exact address of each user, and they definitely know the law in major American urban markets. They can't play dumb in an American court and say "oh I didn't know it was illegal for my residential hosts to rent rooms in SF and NYC!" Like, come on. Judges aren't dumb.