An experience of mine came to mind. Many years ago I met a girl and we dated a little, but I was in the process of moving cross country.
We continued the relationship by phone, the only electronic means back then. And became convinced we were right for each other. I got her a plane ticket and she came to visit for a week. That was enough, it was a mistake, nothing disastrous just when spending that much together time it wasn't right.
Point is I knew her a whole lot better than I think anyone would know someone online, and it still didn't work. Seems to make the odds low for the online thing.
Don't know I could be wrong, but thought this experience might be of some interest.