It surely exists. I've got tons of male friends and I'm feeling comfortable to be friends with them.

I have lots of female friends.

I think what people want to say is that friendship between men and women is very different from man and man friendship (or woman and woman). These people would say that the real friendship is possible only between people of the same sex. Put it simply, sometimes men are unable to understand women (and vice versa) no matter how hard they try, just because the way of thinking is different. Therefore there are things I would never discuss with women not because I do not trust them, but because I'm sure they will not understand. And understanding each other is very important when we are talking about friendship.

This question has been posted many times at Italki. The issue here is that men and women look at friendship differently. Stick to socialising in a mixed group of friends and there will be no mixed messages.

The answer to this question depends on whether or not you're asking if it's impossible to stay "just friends" with the opposite gender without it turning into love, or whether it's hard to have a friendship with them at all in the way that they can be your best friend. Either way, I say, "yes you can". If it's about whether or not guys and girls can stay just friends, I think the people who say you can't that are just people who have no boundaries with or standards for the opposite sex. The more picky you are with someone of an opposite gender in order to find them a suitable mate and/or the stricter you are with how the opposite gender is allowed to talk to you and treat you, the easier it is to be just friends with a person without letting it go any further. If it's about whether or not you can be friends with a guy (like a best friend), I've had many guy friends that I considered to be my best friend, that I could talk to the way I can talk to friends that are girls. In fact, I think my friendship between men was stronger at times, because I felt no competition with them the way women can sometimes feel competitive with each other. So no matter what you meant by your question, I would answer, "it's absolutely possible".