[SwellJoe]

"1. Third party statistics sites like Alexa and Compete are horribly untrustworthy indicators of reality."

They're always wrong. But, from what I can tell, they're usually wrong in ways that are still usefully predictive. If you compare two sites at Alexa.com, and there is a vast difference in popularity (as is the case between Quora and StackOverflow), you can probably assume StackOverflow is bigger and growing faster...even if you can't be sure how big the difference is. I wouldn't want to make business decisions on it, but it's good enough for me to feel comfortable making snarky comments about Quora.

"2. Growing traffic isn't the best way to foster a community. I believe pg has written about this a few times, with regards to communities in general and HN."

But, it is the way to justify $61 million of investment. HN doesn't have to ring the cash register. Quora does, at some point.

Anyway, I find Quora annoying. The community may be awesome, but I don't believe the curators of that community are deserving of my attention or my contribution to their walled garden.

[sesqu]

Regarding Alexa and Compate, you're half right. They're wrong in useful ways, but not the way you suggest. What's important to realize is why they're wrong - sampling bias. So they give an accurate representation of a certain demographic, but the usefulness of that depends on the target audience of the site in question. I don't have any examples at hand, but I've come across plenty of big sites that pretty much flatline on Alexa et al - because their clientele is not welcoming to such measurements, for cultural or geographic reasons. So you can (usually) use them to contrast direct competitors, but I would be wary about quora vs. stackexchange.