I always feel silly talking about it but oh well. I met my boyfriend on Gaia, actually, when the CB used to be pretty normal, just talking in a thread. We kept talking through PM's and eventually through YIM. It was 2 years before he flew up during the summer to see me (my sweet 16 present) and when we met it was surprisingly not awkward at all. Of course he had to go back to Texas but this past summer I went to go see him and stayed with him and his family. I'm trying to set up for him to come where I live for prom, only about a 4 day stay but its better than nothing.
I think if we had met by going to to same school or something we wouldn't have dated, merely from shyness and how his demeanor can be towards people he doesn't know. My only regret is having met so young (me 13, him 14), because it takes even longer for us to build up a scenario where we can live together and such. In March we will have been together for 4 years, but it will be another 4 years until we can live together, because we won't be attending the same college, nor be attending school in even relatively close states (him in Texas, me in Maryland).
My friends are extremely supportive and say we have a stronger relationship than any of them have developed.
So for online relationships, for some people it works, some it doesn't. It's all just preference. Though I do think you need to have the intention of meeting somewhere down the line.