Okay, since Nerdom brought it up, I have to tell this story:
From time to time I teach an intro to outdoor climbing course for Cornell. I once had a student use one of the porta-potties at the bridge and come out complaining about how the "soap" was nasty. Upon further questioning, I determined that she was not joking... she was, afterall, a freshman from long island who had never even been camping. So, it's true, some people do wash up in the "sink".