I have had two very deep online relationships. One that I regretted, one that is currently having problems, but worth all the effort I'm putting into saving it. I got to know her fairly well through talking to her, and we fell deeply in love. Then after about 9 months we met in person, and things just got better. We've been far apart for two years now, but we're still together, and fighting for our relationship. We are so amazingly close when we're together, and have a very strong connection with each other. Even when things are at their worst, we still have a connection, and while I have a tendency to screw things up, she hasn't done things to make things worse for us to this day. And let me tell you things have gotten pretty bad between us at times.
I agree with Tinkleflower. An online relationship can be stronger and longer lasting than an offline one. You have a chance to really get to know
the other person before you get to be with them.