The Utopia Of Friendship?

What defines friendship? What are the basic ingredients that make it work? Certainly friendship cannot be based only and entirely on trust, as trust cannot be taken for granted considering personal issues and beliefs can storm in at any time.

So, where does someone live within the sphere of such relationship when the two common denominators keep on fluctuating under those unpredictable factors and behaviours? What happens when both parties start to realise that they don