I'd read about these services a few years back in Wired -- the one thing that really sparked my interest was mention of a specific gene -- if you don't have it, you can't/won't get lung cancer -- period. As a happy smoker, I'd be curious to know if I was/wasn't prone to cancer.
Before anyone says anything, I know -- "if you're worried, quit, then it doesn't matter" -- but I doubt knowing would change my behavior, it's more a matter of morbid curiosity