Just because you have guy friends doesn't disprove my statement. Chances are your guy "friends" would love to stick it to ya, or vice versa, or its a mutual attraction, but there will always be sexual tension on someone's part. That's why you're friends after all, because there's attraction on some level; whether its emotional or physical, there's a certain quality that attracted you to that person in the first place. And I've had awesome friends that were women, but the only thing that kept us from tearing each others clothes off at the first opportunity was circumstances... i.e., we were both in relationships with other people.
Its a simple fact of human nature and the "friend zone" wouldn't exist without it.