What makes us gay? It seems pretty clear that it's quite hard wired in most gay men. Lesbians, and women generally, have more fluid sexuality. There's an interesting piece in New York magazine about the science behind sexual preference.
One provocative question: if you know a child were gay, would it be ethical to abort it? Or to genetically manipulate it into heterosexuality?
This all goes back to a post I made some time ago about what it is to be different: I called it "Curing the Variant". When is a difference a "normal" variation and when is it a pathology?