This is the perfect solution to The Topping Discussion.

There is an essay out there on human vs. superhuman physiology ("Man of Steel, Woman of Tissue Paper" as I recall) that explains why it should be impossible for Lois Lane to enjoy sex with Superman. I'd assume the same problems would apply with Clark/Lex, which makes me very uneasy indeed around the pairing. (The essay is a hoot but don't look it up if you're easily squicked by reproductive mechanics.)