Enter the Philosopher....
It's good to get some female perspective on this topic, Dragongirl.
*cracks knuckles* This'll take a while.
Just a note beforehand: I'm not anti-homosexual in any aspect, I just think(rather understandably) from a heterosexual male's perspective. So don't expect to read references to guy&guy relationships.
Item 1 -
The idea that men constantly have sex on the brain.
From my own personal experience and interaction with other guys, this isn't entirely true, nor is it entirely false. THOUGH it does fall closer to true than it does to false. While I don't agree with the idea that men are completely hormone driven, I'd say that thinking about sex is our back-up generator when it comes to thinking. We can easily go through long conversations and sometimes day-long periods of time without even remotely touching the subject, but when we don't have anything in particular in our minds, our thoughts tend to drift towards sex, in one form or another. Not to say that all married men think about every woman they see when in this state(more on that later), married guys would think about their wives, dedicated guys about their girlfriends, and single guys - "That redhead's got a nice---that blonde has a huge----DAMN! that's hot!", etc. But in general, we all have sex on the mind when we're bored, some more so than others, some a lot less than the rest.
Item 2 -
Friend Compatability and Spouse Compatibility.
Bear with me on this one. From my experience, regarding guy-girl friendships and romances, guys tend to have prerequisites for each category, wether concious or subconcious. While a woman may make for a nice friend, she may not at all fit a guy's needs & desires when it comes to love. On the other hand, a woman may make for a good friend, and eventually the guy may get it into his mind that taking the relationship up to the love-level may be called for or even expected. Also, perhaps a guy falls madly in (one-sided)love with a woman, but feels nervous about right-out asking for a date, so he decides to first form a friendship, and steadily increase the level of intimacy, etc.
An example from my own life: I am good friends with one particular girl, but we're just friends and neither of us would think of taking it further than that. But then there's this one girl whom I well...you could say that it was love at first sight, for my part. Mind you this isn't one of those "I want to screw the hot bitchy girl" situations, she's a very nice girl who always has a smile, etc.(stopped early to avoid ranting). Not being the type to just walk up and say "Hey, howya doin? Got any plans this weekend?"(not to be crude, just an example), I form a friendship with her and learn that she has been dating this one guy from her home country(apparently met him while visiting relatives) for quite a while. Imagine my dissapointment.

So, not being an ass, I have become really good friends with her over the past few months. However, she has recently revealed that they have just a few weeks ago broken up on a good note, the reason being distance(he's in Eastern Europe, she's in New Jersey, it's understandable). Now I have no competition, so to speak, and well...I'll see how it goes from there.
Item 3 -
The Topic at Hand : Can Men and Women Just Be Friends
Interperetation 1 : Before/Avoiding Entering Sex into the Relationship - To quote George Carlin: "What are you,




ing stupid?"(no insult intended) Of course a man and a woman can be good friends without having sex enter into it. Of course there may(or is likely to) be some sexual attraction, it's a general consensus that once you do something sexual in a relationship, that relationship is changed for good. Avoiding this is something that most men are able to do, the thing is wanting to avoid it. Just to comment, REAL men aren't the ones who crush beer cans against their foreheads, bench 350, and screw everything in sight. Real men are the men who can control themselves, who have this little thing that I like to call
Willpower/Self-Control. If you can simply say to yourself "This is wrong. I want to avoid this. I WANT TO, but it's not worth it.", you should have no problem.
Interperetation 2 : Post-Breakup - Honestly, maybe this is because the only info I get in this aspect is from the average teen in middle-class New Jersey, but....no. While I'm not so stupid as to think that once a couple breaks up they are AUTOMATICALLY going to HATE one another with a VENGEANCE for the REST of their LIVES!*pant pant*....I've seen that post-serious relationship friendship is more elusive than a pudgy Hawaiian man pushing a fruit cart in the middle of the Gobi Desert. Lets face it, if you've exchanged bodliy fluids with someone for a prolonged length of time(outside of a blood transfusion), the tone of that relationship is permanently altered. Once that tone is set, you can't go back to the past and become simple friends. There is always a sense of unease between the two. It may be as extreme as stated above, or it could be as simple as taking the position that having had love between the two of you, neither of you is comfortable having less than that. It's all or nothing. In either case, I don't think so, post-relationship.
Just a bit regarding me since we're on this topic. I'm the type of guy who simply HAS to commit before getting serious, so to speak. I don't go for quickies, one-night stands, etc. If I'm going to be that intimate with a woman, I need to be intimate in all the other aspects of a relationship. I don't know how many other guys are like that, but that's just what I'm like. Bonus to my mindset : My woman will never have to worry about me being faithful.
*cracks knuckles, wrists, flexes elbows, shakes arms, twists shoulders*

ANGCURU HAVE SORE HANDS! Need rest! Go get Iced Tea!
EDIT - small edit for profanity filter circumnavigation. Otherwise, very insightful post. - Henry