I was dumping one time when all of the sudden, I smelled that stink of raw sewage - very close by.
I looked under the next rig just in time to see the guy had goofed up something and his tank was emptying onto his bare hands and all over the ground.
I quickly finished up dumping and got the hell out of there.
On a separate note, I have a place to dump grey (but not black - dumps to storm) at home. The black tank is so big that I can easily go a couple of trips without dumping it so I often just bring the grey home to dump.