This is a very deep question you have asked. As most that have been on the internet for 5 yrs or more know, you build relationships over time. Some meet online and go on to get married.
Although online nor the telephone can take the place of shaking someone's hand face to face, substantial friendships can be built online on a bulletin board or otherwise. I consider many of you aqauintances and some friends. To me, I would invite a friend to my house, but find reluctance in inviting an aquaintance.
You see, all relationships are built on some type of foundation.. whether it be meeting at a herf, a tobacconist, vacation, or over the phone (ie.. suppliers etc.) Although you may never have met them in person, you feel like you can discuss things with them that you would not talk to family about.
I guess it goes back to you as a person and if you are insecure in the real world, or uncomfortable dealing with people in general.
RJ