Is one good friend enough, or do we need many?

In different phases of my life, I have been blessed with many good friends, and at other stages, I have had a few really nice friends. I guess further to another question I asked is, how many friends do we need in this busy world, or is more the merrier? Also, how do you manage your friends, or does each friendship fill a different need/area of your life? For those who prefer only one or two friends, how are you able to keep these friendships in perspective with other areas of your life?