I really dislike bathroom humor. Not because I find it gross or inappropriate, but because I just find it unfunny. It seems like a cheap easy laugh. I do occasionally laugh when someone mentions vomit or shit or pee at inappropriate times but the humor to me is in their own embarrassment/disregard for social norms. Actual fart noises or visual bathroom humor doesn't make me laugh.
On a totally different line of thought, the evolution of humor. The fact that generally the humor of past generations falls flat on the new generations. Are we desensitized to what may have been shocking in previous eras? Are we missing the important social context? Or, a theory I find most interesting, is there a "trickle down" of ideas/jokes where we have all ready been exposed to the central idea of a joke before we hear it, therefore expecting the punch line and dulling the humor. For instance the hypothetical First joke about a mother-in-law would have been very original and funny. Now, the idea of mother in law joke, after being told in countless incarnations, has become so common and widespread that it is expected and not particularly funny.