The average American knows about 600 people.
Paradoxically, I know too many people and too few people. But, as Harold Bloom pointed out, we read literature because we can in a lifetime not know enough people (so -- vicariously we "get to know" all sorts of people we would otherwise never encounter). So, instead of focusing on expanding my social circle, I will continue to expand through my reading. That will have to suffice. Postscript: Does "knowing" people through blogging count? I now know some interesting people.