Elro: What is the problem you see with it?
Well, on a religious level, I think the idea that any sex outside of marriage is immoral is grounded in inspired Scripture, so I'm sort of obligated to think it's wrong on that basis alone.
More personally (And I suspect of more interest to you) I think it's generally gross and unhelpful. Sure, it's fun (Or so I've been told) but it's also a great way to spread disease or get pregnant, or get someone pregnant. There's serious health and lifestyle concerns that, although theoretically mostly manageable, are practically ignored by lots of people. Additionally, I think it's often used as a way of avoiding dealing with emotional problems -- think, "I don't really feel like a man, but if I screw this cheerleader in the butt, then I've gotta be," or "I'm really insecure and have daddy issues, so I'm going to have sex in a bar bathroom with this guy I just met, 'cause it makes me feel valued." No, those aren't
inherent issues -- people can watch out for their health, minimize consequences, and have casual sex while paying close attention for relevant emotional issues that shouldn't be masked by sex -- but they do tend to play into it, even if it's not immediately obvious, even to either participant. And I'm not going to get into the fact that casual sex can be dangerous ("Oh hi Craigslist sexbuddy!") or take place with questionable levels of consent.
Also, on a personal level, I think it's generally gross, and I find myself less attracted to and respect less girls who engage in such behavior. (And on an equal level, respect less guys who do so) I think sex really is something that should be reserved for marriage, and I think they really worsening themselves in some perhaps indefinable way by doing so. Now, of course, I have done and do things that worsen myself too, so I try not to be overly obnoxious on this point -- but just because I shouldn't point fingers doesn't mean there isn't something that deserves to have fingers pointed at it.
So it's sort of hard for me to have a positive perception of something that I think is generally gross and typically associated with an unhealthy situation in one way or another.