Oh they can work, when I was but a naive teen I was in one and it was nice on the whole, I don't think it was harmful in any way that's for sure. However like everything I get into it ended horribly. ! But all my relationships kind of do.
The rule for meeting people on the internet: The odds are good, but the goods are odd.
My uncle met his wife through the internet. And it wasn't through a match making site. They both had these blogs (I think on livejournal?) and they started commenting on each other's posts. Then they started chatting together for a long time, and later tried dating. About a year later they married, had twin boys, and moved to London a couple years after
So yes - internet relationships can definitely work. Of course this doesn't mean all of them do, but the possibility is there and well, that's something too.