I need to present a different viewpoint. I stopped hosting WarmShowers after I had a difficult interaction with its founder/director. I had been hosting for a number of years - usually I check the person's background. There was a person who had recently pled to reduced charges after a fraternity hazing that was nothing less than sexual assault. The person bike touring was not just a member of the fraternity, but the supervisor of the pledge class. The news was published by the university involved and the charges and pleas were readily available in major news outlets. When I contacted the WarmShowers director, he indicated, I believe, that he did not operate a vetting agency.
As a survivor of a violent assault, I do not wish to have someone like this in my home. There may be numerous people who have had convictions for violent crimes out there - some may have even stayed at my place. Many may have acknowledged their wrong and made amends. But the core issue of safety seemed to have been brushed off by WarmShowers. All the organization needed to have done was to have contacted the person in question and asked whether or not the charges and convictions were valid. And, if so, to have asked him to remove his name.
Yes, the vast majority of bicycle tourers are great people - - but it only takes one. The internet is a great tool, but as with Craigslist - it can attract sociopaths. I consider myself a generous host - shower, dinner, laundry, and lots of local info if desired. I have rescued dozens of stranded cyclists in the mountains - snow, wind, cold, breakdowns. But this incident with WarmShowers underlined the need to use prudence.
And, ultimately, I do not feel that WarmShowers does.