What makes FB interesting?

Yesterday facebook admitted that abouy 80million accounts are and out of which 46million accounts are duplicate. Rest are either pets account or some nonliving object account created by users. Yet it still has huge amount of people to surf on. In time since its 2003 inception at Harvard University, it has picked up the market since 2009 and made tremendous impact on people. Every company ever ads now have a white f with blue square logo on it as if facebook are their main sponsor. How come facebook dominated the market in such a great way. To make it interesting many features are either picked up from here and there. FB wall is like twitter. Most if I compare it with myspace would look same. People sharing info on wall. FB mania has also taken over the phase of lives too as most people just text their current info with a single message. What its like a current generation that use digital communication to be close with its close ones. How did people came to know about it so much. Why not people came to know much about myspace or Friendster. What could be its reason for its success.