I was concerned when there was a guy asking for lodging who had pled guilty to serious sexual assault charges as a fraternity officer in college. I contacted WarmShowers office and they said it was not their responsibility to vet users. I found their response highly cavalier given the serious problems share-sites have had with safety. 99.9% of the encounters may be perfectly fine, but it only takes one. What troubled me was this was a person with a verifiable, dangerous offense - and WarmShowers basically said, "So what?" I have chosen not to host since then.