Friend zone: How many “besties” do you really need?

I must confess that I have never really understood the concept of a ‘best friend’, or as young people today would call it, a ‘bestie’. How can you choose one friend above all the others who are close to you and proclaim him or her to be the best? How do you decide which one of the many people you love and cherish deserves to be given top billing? And how do you justify downgrading all the others who care for you in the process?