I certainly beg to differ with all the 'no's but I guess we need to define what counts as an online relationship.
My boyfriend and I met online two years ago. We were friends for a good eight months and we visited every so often. When we decided to date, we were living across the country. I decided that I wanted to make it work and I was in a very in between stage in my life, so I decided to put some funds together and move to where I live now. I would come out and see him for a week every six weeks. After six months of that, we moved in together.
Under normal circumstances, I would understand people saying, "Holy crap, that's a terrible idea" but we've been living together for a year and it's the best relationship I've ever been in. We have our problems, but I had far more problems than guys I had dated "in real life."
Now if you're talking about relationships that are strictly online and never have face-to-face contact, they can only go so far and are generally doomed to fail. Truthfully, my boyfriend and I probably would have too if we didn't make some changes and sacrifices. But to say to someone who has legitimate feelings for someone else, regardless of the locale, that their relationship isn't real, sorry, tough on ya? That's a bit cold and inconsiderate to me.
All relationships have value and meaning, and you can't define them without being in them. Do they all work? No, of course not, and people who have online relationships have the absolute toughest jobs. I don't see them working in the end until the distance has been closed, because that's human nature, but it's still a relationship -- you're still relating to someone else.
Sorry if this came off insulting, but that's just how I see it.