I agree 382% with Liamson. Distance allows for our minds to fill in the blanks. Especially when we want to like someone we fill in the blanks with rainbows and puppies. I, personally, fill in every blank with the worst things of which I can think. That way if I were ever to meet someone casually my expectations would either be met or exceeded. Anyway, I also agree with Sooner28 - meeting someone online and then expanding from that after meeting in real life changes the game.
Even skype and the phone allow for hidden qualities. It's just not enough. And honestly, with long distance relationships there is a whole slew of other things to consider related to trust, daily life, etc.
I have nothing against those who try it out... just a ton of hope that they are cautious and realistic.