I have about as many female friends as I have male friends. I am completely straight, but almost all my friends have at one point genuinely asked me whether or not I'm gay. In addition, most of my female friends tend to view me as someone who could never see a girl as anything other than a friend, despite the fact I have a girlfriend. But on topic, I see nothing wrong with having close friends of the opposite sex, though it has the potential to complicate things when you're in a relationship with someone else.