Doesn't it all depend on context? I mean, that could come off flirty (in an awkward, dorky-line sort of way) or kinda creepy all depending on who said it and how it was said (or written, as may be the case).

As for the question to the boys, if I may put my girl two cents in I think that really depends what type of sexual question is asked, how it's asked, and how you feel about the individual person who is asking. Sometimes something just comes up in conversation and you happen to feel comfortable with the person you're talking with (be it on the first or fiftieth date)... sometimes not so much. Just consult your inner creepy-o-meter because, alas, I don't think there are any set rules for this sort of thing.