A friend is someone you connect with, someone you share with, someone you have things in common with. How you meet or how you communicate is irrelevant. My grandpa "met" his bride through the mail - they never laid eyes on each other until the day she got off the boat. But through their letters to each other they learned to love one another and knew that they wanted to be together. They were "posting" long before it took this form!
People frequently refer to the "real" world, as if this online world were not real. How is this any less real than the parents that I have gotten to know through my boys' many years of baseball? I am still real, you are still real, and we are sharing about the things that mean the most to us. Doesn't get much more real than that!