Close Friends, Friends and Acquaintances
I think some of us are more social than others. And because some of us are not public with what we do we tend to be more private and reserved for fear our secret be revealed.
Even though I am public with what I do when I go outside I'm not very public on the web. I tend to keep my shields up to some degree. And in public I'm the same.
I also keep a very tight circle of close friends that I believe have my best interests at heart. Next group are friends I have met in person and have shared some time together. On the web I think of friends as acquaintances. I only know them through what they write. That does help get to know a small piece of that person, but I prefer a real life meeting.
And finally how much time do I have to commit to that person? Generally what you put in is what you get out, but not always. There is only so much time I can commit to my friendships, only so much of me to go around. :D