Everyone has questions. Questions can be googled.
Granted, Googling stuff is hard.
Even though you can just stick a question into Google and get some reasonable feedback, it's still hard to know who to trust: I read most students have no clue on what to trust when googling for school assignments. It's not taught there, they're just expected to know. And it's one of those things that is crucial to fully understand things in the society of today.
Of course, people want definitive answers. If there's a definitive answer for something, it's probably in a place like wikipedia.
For something that doesn't have a definitive answer and which can be discussed, there's discussion forums like reddit and HN that a great for this purpose.
In my mind, Quora solves very little, and the way they force you to login really irks me – information should be free. (Just make it publicly accessible already! Make dumps and APIs available like wikipedia. Make it free!) And then there's all the other issues the author describes in this article, especially the inane questions.
I have to say, lots of interesting discussions have happened on Quora - mainly due to the participation of interesting people, not random 13-year olds. That's still a huge accomplishment and why I hope Quora sticks around, but more in form of a general discussion/opinion/experience platform.