Well, it doesn't spread the same sorts of germs as fecal matter (hepatitis for one), but I can tell you I'm not too crazy about public hot tubs for that reason. I had some friends who had one and after having a party they found tomato peelings in the filter.
I've noticed on long runs that if I had to pee at the start I sort of stop needing to after I work up a good sweat.
I don't think ANYONE here is going to claim it's okay to crap in the shower. LOL