The world's biggest social network Facebook says the average distance between two people in the word (i.e. the world of facebook) is about 5 person. That means by hopping the friend list of any random 5 people will connect you to almost any other people in the world. Being specific, the world population in 2011 was counted to be 6,973,738,433. This statistic is mind boggling. You can know 7 billion people just by connecting with link of 5 people. The essence of this fact is we are connected together. All of us! And therefore the world is round.
There is another fact hanging around: the average number of Facebook friends is 130. Interestingly, other research shows most adults have 'only two close friends'. So who are the rest of them? I don't know.
I don't know why we got connected. But the floating energy from the distance galaxy in the form of cosmos has made us connected. Sticked together.
The answer to your question is really hard to answer. Why are we friends? To find answer, I ask to myself and I get 100s of reasons and justifications, but none of them satisfies me. The only fact remains is: We are friend. Good or bad, in fight or in laugh.
We know our limitations, we know our capabilities, and we share everything we know. I hide something of mine, and you do the same. But at the back of mind, we expect to share that.
We don't want to interfere on personal business but that doesn't happen. It feels good when we interfere in those personal businesses. Though angry we may look, but deep inside we are satisfied.
You may be blue and I may be yellow, but together we make shade of happiness!