Don't you just hate it when you're taking a dump and you plop one out with enough velocity that the water in the toilet splashes up into your bunghole? I hate that, epecially when it's a public toilet (like here at work). If it's my own toilet, I don't mind as much.
Being a girl, and only in some toilets...that happens when I pee. I don't know if the toilet water is too high or what, but its creepy.
i don't care so much about public vs private toilets, but it is exponentially worse when the water is already yellow at the time of splashing.
I have also found some toilets to be anatomically inadequate for the comfort of males users. The touch of cold, wet porcelain is equally as disgusting as a splash in my opinion.