As we’ve seen from the recent Quora wars, the Q&A space has come into its own in the last couple of months and this week we’re seeing reports of crazy growth in yet another contender, Q&A site Stack Overflow. A blog post called the “State of the Stack 2010 (a message from your CEO)” reveals that the StackOverflow.com site has grown 131% this year from 7 million to 16.6 million monthly unique visitors. Stack Overflow has also grown 129% in terms of page views from 31.8 million views per month to 72.8 million per month, according to Google Analytics.

Last time we checked in with Stack Overflow it had just crossed the 10 million mark on Quantcast back in November. But co-founder Joel Spolsky is skeptical of  “notoriously inaccurate“ traffic gaging systems like Quancast, Google Analytics and the terminally unreliable Compete and holds some other more tangible success metrics close to his heart.

Says Spolsky,

“The true measure of success for any Internet company is how often people come up to me in swank hotel lobbies and offer to buy me meals, let me use their corporate jet, etc. But since there is a great deal of disagreement as to how to measure that, we track a reasonable proxy called “eyeballs,” on the theory that if a site is useful, people will load it up in their browsers and eyeball it.”

Spolsky is right, there is a direct correlation between the amount of random people who approach you in hotels asking for stuff and how confident you should be about your success during family holidays, especially if you’ve already got a flattering “Forget Quora!” profile in the New York Observer under your belt. As proof of Stack Overflow’s coolness, Spolsky writes that he’s  pretty sure “ALL the programmers in the world use Stack Overflow” (source: completely made up).

But aside from traffic and million in funding and sycophants and the fact that if it grows as projected the company will be “bigger than Facebook in 15 months,” Spolsky has yet another metric for success, and this one (he swears) is the most important, he swears. Percentage of questions answered is the holy grail of Stack Overflow, and as of right now three of the sites (Cooking, Photography, and English) have a 100% answer rate, which means at least one user thought the question was respectable enough to pass muster and garner an upvote.

Indeed Spolsky and his co-founder Jeff Atwood are committed to answer excellence and recently started a program to send their power users to industry conferences as a way to gain knowledge and further evangelize the sites. Stack Overflow and the StackExchange network don’t tolerate subjective or conversational questions either, which is a boon for people who want to browse the Apple topic with out having to read anything inquiring about Steve Jobs’ health, myself included. Hallelujah.

“Essentially, we’ve already learned how to deal with ‘big city problems,’” says Spolsky, referring to the network’s overall 90% answer rate. “We think of Stack Exchange as being more like the reference section of the library where you go when you really need a specific answer and you have to talk to experts; all the other Q&A sites are structured more like social hangouts where you shout out your question in a crowded bar and hope there’s one person who hears it and knows the answer.”

And on that note, the Q&A showdown continue.

Image: 3-Fach

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