Thanks for the information (it's 1:35am so I might just leave it for later to deeper read into it), although my question wasn't so much on "sex" but on "gender" and the fact that, after all, one is referred to as either "mr" or "ms", which in a better world it'd always be what the person identifies as. And really, if you're not telling what you are between "mr" and "ms" then the logical conclusion is that you're hiding it.
Of course this can come from my limited understanding of the world (and the fact that I'm studying to be a sysadmin and I'd like to keep that as a yes/no field on future databases), but I really don't see how someone would be adressed in a different way - hell, as far as I know, Spanish language doesn't have another gender.