I didn't read all the responses, so I'll just throw my opinion out there.
My mom and stepdad met online the early winter of 2006. They started out as friends, chatting constantly (I'd always hear my mom's laughter in her bedroom but didn't realize she was talking to someone she had never met before). They met after a few months of friendship--having never even seen photographs of each other, and it was love. They met the spring of '06, moved in together by the fall of the same year, and were married the fall of the following year. To me, it was weird. It was all too fast. My stepdad didn't seem like my mom's type, and I didn't see what she saw in him. However, I can also say that I have never seen her happier. He is truly her soul-mate and they never would have met if it wasn't for the internet. (He lived in another state originally). 6 years after meeting, they are still together, and happy. That's not to say they haven't had their issues, but because they were both honest online, they worked.
I've also seen so many failed online relationships. People meeting here even, marrying, and then getting divorced only a short time later. When you talk to someone so long online, you tend to imagine them in a way that might not be fitting. It's not that they're doing anything... it's you. You make them out to be sweet and cute and flawless because it's easy. You put expectations on them that they'll never succeed in fulfilling. You don't get to see all of their quirks through typed words on a screen--quirks that could potentially drive you crazy.
I do not think that long distance online dating works. If you have the ability to see someone in person after a short while of talking online (maybe a couple of months), and then establish an in-person relationship it could work. But long distance chatting, meeting a couple of times in person, and then getting married... probably not smart.
Even me, I met my best friend online... We talked EVERY day for 3 years, and took a week's vacation together after a year and a half. During our week vacation he seemed exactly the same. A year after that, I went to visit him for longer. I stayed with him for three months last summer and our relationship changed dramatically. Are we still friends? Of course! But I don't hold him in the same regard as I did when we were just online friends. Admittedly, I had liked him as more for some time, but those feelings completely vanished. I saw him in his world. I saw all of his quirks and how he is in person vs online. He's the same, yes, but he's also very, very different. I think we all are.
Personally, I don't think I'd ever date someone I met online, unless they happened to live very close to me. I need to be able to see them in their world, and I need them to be able to see me in mine. Plus I like the close touching/holding hands/kissing bits of the relationship and couldn't take not having that for long periods of time!

Haha