the problem with this whole issue is that the more seriously we discuss it the more we are likely to entirely miss the point. it's like Sigmund Freud trying to analyse (in a 400 page volume) what makes a joke funny, or what it is about someone slipping on a banana skin that makes us want to laugh. He might even succeed in his analysis but you can guarantee we won't be laughing at the end and so his definition - correct as it might be - also misses the point.
One great problem that Christians have to wrestle with (alongside anyone with a tendency to take life too seriously) is, that in our attempt to relate every tiny aspect of their lives to God, and to justify everything with a suitable quote from the bible (preferably Paul) we miss the point. Moreover it won't take us a single step closer to our goal.
Conversely, the wonderful thing about the average non-Christian human being is his ability to differentiate between Things that Really Matter and Things that just sound as though they Really Matter. Because he is not focussing on any point at all he is far less likely to miss the real one.
When I went to music college, in the pursuit of 'mastery of my subject' I went through many years of not liking music any more. I knew how it was put together; I could play some of it; and I could even write it myself but I didn't want to because the learning about it had completely robbed it of all the meaning that it had previously had for me.
I think Christians go through a phase like this and for some it can last a lifetime. It's a misunderstanding though, and a very fundamental one. It's probably also a necessary phase though and has to be gone through.
There are some problems about the Christian life which don't improve by studying them and sex is definitely one of them.
I am reading Matthew's gospel at the moment and over and over Jesus rails against the pharisees and saducees who take life so seriously that they end up mistaking goodness for evil and evil for good. This is not some uniquely Jewish problem, it is a problem for all of us.