I have in the past slept with girls I would have classed as friends but I wasn't pursuing them, they came onto me. However, when we split up, that was it, end of friendship. I have female friends in my social group but although some are good looking, I am not attracted to them, they don't hit the right buttons.
Like I said, When Harry Met Sally, a man and a woman cannot be friends when there is sexual tension, you become lovers at that point due to the attraction.