This is something which really fascinates me.
I do agree with the notion that there really isn't that much separating close friendship and romantic intimacy. I really believe that friendship is the foundation of a romantic relationship. Both of these are pretty close together in terms of emotional connection, the only real difference is the aspect of physical intimacy.
I do have some guy friends, one which is particularly close to me. I don't think these kinds of friends always fall in love or anything of the sort. It's definitely possible, and a lot of relationships start that way but not a certainty in every case. I think it's completely possible to be friends without anything romantic getting in the way. But despite saying that, my experiences have been mostly that friendships never stayed platonic. Usually one of us developed feelings for the other and the friendship disintegrated.
Definitely possible to be just friends, usually one ends up falling for the other though I think.