They aren't for everybody, but for those who are able to spill their soul through text to each other with that special someone they click with, and have deep rewarding conversations, regular video/voice chat, and they have a heck of a lot in common, and a lot of patience, I say go for it!
Just because it totally doesn't work for one person you know and they say only negative comments about them, or your parents' friends don't understand, etc. It does not mean it's the same with all. It's an individual thing. Everyone has different emotional needs in a different order.
And not every in-person relationship is long-lasting either. I don't know why people are so quick to jump on peoples internet relationships so quickly if it doesn't work out with them. People who date in person break up all the time.
I've been in a long-distance relationship with my guy for almost 4 years. We've met in person 5 times, and yes, all those years ago on that first meeting, he was exactly like the impression of him I got online...except more real lifey.
It did help that we started as only friends, and moved extra slow. We took the time to get to know each other at a slow, "boring" pace over the internet so there would be no surprises.