I'm not a huge fan of TripAdvisor because they allow negative reviews under anonymous monikers, a form of bullying. Nevertheless, this recent survey they're promoting is snarky fun ... a summary of the 10 U.S. hotels rated most negatively by their readers. This procedure qualifies it somewhat, in my opinion, since it's the net result of many reviews rather than just one or a few unknown individuals.
Dirtiest Hotels - United States
as reported by travelers on TripAdvisor
http://www.tripadvisor.com/DirtyHotels
