Everything's temporary. The question is the timeframe. The peak for facebook doesn't come until kids move to something cooler, and even then it can be a pretty long slide into irrelevancy.
What's the next cool thing that's going to draw people away?
I agree. Facebook will have challenges. How long they survive will depend on how fast they can react to these challenges. They have, however, a '600 million users' advantage...
What's the next cool thing that's going to draw people away?