Guys and girls can't be friends. There, I said it. Oh sure, you can be tight with your bestie's boyfriend. Or have a great rapport with one of your exes, having realised you're no longer attracted to each other. But these friendships only work because of pre-existing factors - i.e. he's taken (by your best friend), or you gave it a go with him, but the sex was shit. So there's really no option to be anything but friends.
On the flipside, I have never come across two single, heterosexual members of the opposite sex who have managed to sustain a friendship without a remote trace of sexual curiosity from one or both parties.
It's natural instinct to survey the opposite sex for potential mate value. And a friend of the opposite sex couldn't be a more worthy candidate. I mean, don't the qualities we like in our friends form the basis of what we look for in a partner?
You see it happen all the time. A supposedly platonic relationship turned passionate affair after a few drinks at the pub. The confession of undying love from one party to the other, often only to discover it is unrequited. Or the most heartbreaking scenario - when feelings are kept to themselves, stewed over for years, but obvious to everyone around them. And why are these feelings never publicly acknowledged? Because the girl or guy is terrified of ruining their 'friendship' with their best mate, AKA the love of their life.
Now don't get me wrong, there are plenty of male-female friendships where the romantic avenue has been travelled down, only to discover they took a wrong turn. There may be no hint of it now, but my point is at one time, if only for a drunken moment, there was sexual experimentation or speculation from one or both parties in question.
The friendship gig simply cannot play out between single man and single woman, as the elephant in the room will forever be present... you get along, you make each other laugh, you agree on the big issues, you've got each other's back... so why are you 'just friends'?? Perhaps you should grab a beer with them and find out..