Is it possible to have a best friend who is the opposite sex?

[El Jefe]

I have pondered this, and I think it is virtually impossible. I have had 3 girls who I would consider best friends at points in my life, but all 3 came to a crashing end. They eventually came to a part where they wanted a dating relationship and I did not. I think for a guy to have a girl who is their best friend, the guy either has to be gay or the girl has to be married for it to work. At least in the kind of girls I deal with.

The most recent was a girl I posted about on here last year, we had known each other since we were kids. We dated for a couple of months while she was in her senior year. Then I cut it off when she went to college, and I thought things were cool. We were best friends up until this year, she has had a boyfriend for the last 5 years, and we were fine. Now that I have a girlfriend, she actually told me I either choose to date my current girlfriend or her friendship. So I chose to date this girl, and we have not spoke since, and I never saw it coming, she completely changed once I found somebody. I couldn't have cared less when she got a boyfriend, but apparently when we agreed to just be friends she still deep down wanted something more.

Anyone have any thoughts on this, Im sure it will change as the age group of the girls I am around continue to grow older each year. All of these girls except one are in college still FTR.