The problem was that there was no barrier to entry, and therefore there was no way to prevent people from misusing it.
The intellectual value of Quora dropped as more and more people who had no reservations about posting inherently useless questions joined. If there was a system for filtering out questions from less authoritative or knowledgeable figures, they could have prevented this.
Ah, now how does one find the sweet spot between this and say Stack Exchange? Many times, I have heard users complain about the barrier for Stack Exchange and overzealous moderators. There is not really a way to please everyone.
I never really understood how moderation works on Quora so I assumed there was none. Not to say that I hate Quora (I like it a lot), I just feel there is nothing preventing it from becoming Yahoo Answers in a couple years time. No barrier, no moderation.
Moderation is pretty active on the site, in fact, users who have interacted with Quora moderation consider the site to be heavily moderated... you are right -- there is a sweetspot somewhere, but even that is just a sweetspot for a small subset of users. Nobody will ever please everyone.
The intellectual value of Quora dropped as more and more people who had no reservations about posting inherently useless questions joined. If there was a system for filtering out questions from less authoritative or knowledgeable figures, they could have prevented this.