While said cavorting can often be hugely bilateral, things like RealDoll Rental in Japan make my teeth stand on my hair.
Prolly NSFW link, BTW. Banner ads with boobies.
While the concept of rental sex toys carries with it some degree of squick, I would imagine that they are "rehabilitated" in the downtimes with a bottle brush and some ham sanitizer, and are probably delivered to your door somewhat cleaner than a dog's mouth.
(Hark! I can hear avindair cringing from here!)
People get squicked by things of a sexual nature, particularly in the bodily-fluids category. It makes it an easy target for squicking like killing a puppy makes for a shortcut to tears in an after-school special. For instance, if I want to make a creepy-guy character, I have him jerking off into a test tube, labeling it, and putting the test tube in a rack that as the camera pulls back has hundreds and hundreds of similar test tubes. I know nothing else about this guy, but instantly the sexfreak label is upon his forehead like it was seared there by a cattle brand.
Now if he was drawing a vial of blood and doing the same thing, it wouldn't be nearly as creepy. It could be worked into something creepy, but it does not squick the way man-mucous does (thank you revdj).
I find that particularly interesting. Consider that blood is almost entirely meant to stay on the inside, where love-chowder is almost entirely meant to be on the outside. Blood usually indicates pain, while yank-yogurt is almost always associated with pleasure.
And I have now lost the entire purpose of this post other than finding colorful slang terms for jerk-juice.
Time for the weekend!