I've spoken about this at length with friends of mine, actually, and concluded that you can't really be friends with someone if you are trying to ingratiate yourself to them. Excluding that, I don't think sexual attraction is incompatible with friendship at all.

I do think it's very important to disentangle sexual and romantic attraction. If I'm infatuated with a girl who sees me only as a friend, to say that I am "just friends" with her rings of dishonesty. I think the "nice guy" stereotype serves as a demonstration that many young men do have this sort of one-sided infatuation with a supposed friend.

But with regards specifically to sexual attraction (not that the line is clear) things seem easier.

For one thing, there's a difference between actively being sexually attracted and simply finding someone sexually attractive. Actively wanting to have sex with someone seems incompatible with friendship (given the ulterior motives and ingratiation) but simply being open to the idea of having sex with them is not.

I remember watching a video with the premise that men and women can't be friends, in which young men in the company of female friends were asked if they'd have sex with those friends. All of the men answered yes, and the conclusion was that men and women cannot be friends. I think this conclusion is erroneous; rather, men are perhaps generally more willing and relaxed about sexual interaction (a point which hardly needs to be made, really).

Take this scenario: a female friend of yours walks into your room completely naked and says that she wants you to have sex with her. I think that answering yes does not imply that one can't simply be friends with such a person.

So: guys (and girls) can find each other attractive and still be friends.

I have a friend. We are close friends, but nothing more. We talk about all sorts of things - including other people we like and/or are dating.

We've also spoken about sexual attraction between friends. We've had sex, and (I believe) we're both open to potentially having sex again in the future. But neither of us has any romantic feelings toward the other, and in all other ways we are just friends. Crucially, we will probably still be friends even if we have never have sex again (and had been friends for a couple of years before anything happened between us).

But, of course, it is not the same with everyone. I have another friend with whom I have discussed similar things; we almost had sex (I, correctly, decided not to fully have sex because of how I predicted she would end up feeling). We've since spoken about the same things and she has admitted that she's not sure she can have friendship and no-strings-attached sex without potentially developing some sort of greater emotional attachment.

So I think that men and women, even given sexual attraction (mutual or otherwise) can be friends. This doesn't imply that all such people can be friends. But I do really think that one of the important elements is ingratiation and having an ulterior motive, which don't really work with friendship.