Best friends in LOVE?

I don't think best friends should fall in love. There, I said it. I always used to admire people who had someone of the opposite sex as their best friend. You know, no feelings, just pure love in a way that is not attraction kinda thingy. And I always used to shake my head when I eventually find out that those best friends turn into lovers. It is not that you should not fall for your best friend, it is just that...why? I mean, this is a person that knows you so well, what makes you tick, what is your flaw, who you really are. So, is that why then? Because its easier?
Trust me, I am not judging. I am merely trying to understand something I don't see myself doing. I think love is something that is risky and getting into a relationship with your best friend means putting that pure friendship at risk. What if things don't work out? Is it possible to go back to being just friends?
Well, when you fall for someone, there is no reasons, no explanations, no fear...just love. Purely blinded love. So ya, I don't see myself falling for someone that I really trust and treat as a close friend because I need sparks. I believe in the magical aspect of love. I believe that love has 8 stages. But then again, I am just the kinda girl that thinks a prince is out there waiting to sweep me off my feet.
So, best friends in love? Neh, not my kinda thingy.