"2. it would be difficult for it to become as popular as facebook because there are alreasy [sic] lots of social graphs in facebook already established."

A few points to consider:

1. I'm not an early adopter, of anything, ever.

2. I've managed to mirror 100% of the Facebook contacts I give a shit about in Google+ in less than 24 hours, with substantially improved organization & compartmentalization, not to mention a noticeable lack of ads or Zynga spam.

3. A full third of my FB contacts have requested a G+ invite as soon as they heard I was already in.

4. All of the people I've invited or otherwise added to my circles are active in their G+ accounts.