My contention is that the average value per user of Twitter, Facebook, Foursquare, Pinterest, Instagram, Yelp, and Youtube is $56.
You take the average of those and you're probably looking at a pretty decent ballpark for the value per user of a website that depends on user-generated content and that people use every single day.
At $145 per user, Quora is almost THREE TIMES that average. If that's not an over-hyped valuation then I don't know what is.
Quora has pretty rich content and while they'll never have a userbase like facebook i don't see why the value per user number is wrong