Can we still be friends?

I have a few questions.

1. Can members of the opposite sex maintain a close, yet completely platonic friendship?

2. Is it possible to have a physical relationship with someone without either party getting attached?

3. Once the line has been "crossed" is it possible to go back to the way things were?

From my recent observations of my friend's personal lives it seems like the answer for all of the above is a cynical, straightforward no. No. NO!

So if we have the answer/result/solution to the question why must I digress further?

Because often the explanation offers much more than the answer itself. 

In the end it all comes down to emotion. Perhaps I believe that a straight out NO is the answer because I am a rather emotional person. That means that I wear my heart on my sleeve. I cannot feign happiness, consideration, cannot hide my hurt. So for me that means if I have any kind of interaction with one who would provoke emotion, I must have no more unresolved feelings, no regrets, no hurt pride, nothing. I cannot feel anything for this person anymore. 

I often used to wonder why my fellow teenage classmates used to hook up regularly on weekends with their friends. Why not just go out with them? Then I began to think that if you are friends with someone of the opposite sex and you get along with them well, and they are rather attractive, then of course there would be temptation there. For those who have no inhibitions about fulfilling their physical desires it wouldn't make sense to refuse. So if you spend lots of time with someone and ENJOY spending your time with them, whilst all the while being completely aware of how they look...something is BOUND to happen.

So what happens when a good friendship crosses the line? I believe that if there is no emotional attachment then it is possible to go back to being friends. But there is rarely a mutual indifference about the matter. It is also difficult to forget about the incident if you are friends with the person because you have to see them all the time! 

The movie "When Harry met Sally" was about these very topics. The silly thing was that they actually ended up together after hooking up! That was meant to be the happy ending and it was a wonderful happy ending! However, sometimes I wish the happy ending was that they could move past their attraction and maintain their friendship. As the saying goes "lovers come and go but friends are the ones to pick up the pieces". Losing a friendship means losing someone who will be there for you in the long run. It's just not worth it.