The only times I ever remember anyone asking me anything like this is when I really didn't know the person much. Luckily for me, my close friends are mostly married now and the worst activity similar to those you mentioned that any of them are doing is smoking (at least as far as I know). The hesitation to be completely honest would mostly kick in when a close friend is involved. Most of those types as far as I'm concerned are already taken. For anybody else, I don't see myself caring to "protect" anyone, and I would just tell it like I see it.