The Ladder Theory

After I posted about the Attraction Zone Theory, a friend emailled me a link to the Ladder Theory. It explores how men and women are attracted to each other and discusses Why Men and Women can't be friends (the whole 'When Harry Met Sally' explaination).

The one thing I am in disagreement on is the 2 ladder theory for women. This theory elimates the situation that I strive for. Sex with my best friend. Apparently bad things happen when you move from one ladder to the other. The guy ends up falling into the Abyss.

Why should you have to settle with one or the other? I want it all.