I have had like 2 e-crushes in the past. One was mutual, but we didn't go through with it (heck, I was 12). Another was one-sided, but she didn't like me back (I got friendzoned basically). She then got in a e-relationship, even met eachother, but ended up breaking. She was also from Brasil, so we were basically one ocean apart lol.
Long story short, I never dated in the internet, but I know people who have and know their relationships. My opinion, based on that, on my general relationship experience and my Psychology knowledge, is that they very, very seldom workout, specially when the distance is great and the means to get together are little. Physical presence and contact is essential to a relationship. After all, it is (in crude terms) the process that leads to mating, and you can't mate without being with each other.