Stack Overflow Rides Experts & Order to Q&A Success

Q&A sites are grabbing the spotlight thanks in part to the emergence of Silicon Valley darling Quora, which has become a destination for many tech luminaries and could be worth $300 million. But the genre is still hampered by a lot of bad answers and unanswered questions. Taking a somewhat different tack from Quora is New York start-up Stack Overflow, which has been growing rapidly by focusing on specific content niches.

Stack Overflow, which was originally spun out of developer Joel Spolsky’s Fog Creek Software, reported last month that it more doubled its unique visitors last year from 7 million to 16.6 million, and in the last month, reached 19 million users to crack Quantcast’s list of top 300 sites. The company says its success stems from creating an expert community in which few questions go unanswered, and virtually all answers are of fairly high quality.

Started as a forum for programmers, Stack Overflow has blossomed into a broader network with 43 Q&A subject areas available now under the umbrella of sites known as Stack Exchange. Funded by by an all-star team of investors — including Union Square Ventures, Ron Conway, CEO Chris Dixon and former Flickr founder Caterina Fake — the site has grown from three full-time staff to 27 employees, occupying a floor downtown near the New York Stock Exchange. In addition to growing its Q&A business, the site is also poised to change the job-search game as it updates its career site to help mate its growing community of experts with jobs.


Founder and CEO Spolsky said in an interview that the secret to Stack Overflow’s success has been its push for high-quality content and its decision to segment the service into well-defined verticals. By limiting the domains in which questions can be asked and stocking the existing sites with knowledgeable users, it helps focus the Q&A process, making it less of a free for all, he said. That’s one of the problems faced by many other sites: Questions are all over the place and many don’t get answered because they don’t get routed to the right people.

Stack Overflow’s limited approached has helped the site boast an impressive answer rate of more than 80 percent, and in some vertical subject areas, well over 90 percent. Unlike other Q&A sites, Stack Overflow polices its questions aggressively, weeding out queries that lead to subjective answers or hard-to-quantify answers. The goal is to address questions that have a clear answer, Spolsky said. Community managers and members can vote to close down questions that aren’t appropriate or they can try to edit them into shape.

Stack Overflow boasts about 760,000 users who contribute to the site and is very serious about building a core community of experts. By creating channels around a specific domain and rewarding the best contributors with reputation points, Stack Overflow looks to foster a community of smart users who can bring a lot of shared knowledge to bear on a question.

“If you go to ask a question about physics, you don’t go out to a football stadium and shout out ‘Who can answer my question about physics?,” said Spolsky. “What you’re going to do is go to a university physics department and try and find someone to help you there and our idea is to build those departments.”

Newbies can wander in, but the site is driven by a critical mass of knowledgeable users, Spolsky said. To that end, the site has eschewed social networking conventions like letting users follow each other, the way Quora does. It also lets people sign in with fake names. “It all comes down to: Do you know the answer?” Spolsky said.

Stack Exchange, which covers a variety of non-technical topics including photography, cooking and English, is now growing faster than Stack Overflow as it reaches into new areas. The network is now up to 1.5 million monthly users and grew by 51 percent in December. But while it opened up with Stack Exchange, the company has applied its quality control on that process as well. In an open voting system called Area 51, Stack Overflow takes submissions and votes on potential new sites. It requires more than 200 users to commit to the new subject area to ensure that it has enough experts when it goes into beta. Stack Exchange is now adding a new site a week and is looking at all manner of subject areas in which some kind of domain expertise can be established.

Stack Overflow gets its revenues from advertising and was actually profitable last year before its big push with Stack Exchange. But Spolsky sees a bigger opportunity to leverage and help its community of experts. The site is about to relaunch its Careers site, which will expand its programming job listings to other subject areas, helping its experts in different fields find jobs and contract work. The idea is to help the community leverage their passion into better jobs, while getting a small cut of the action. And it encourages more involvement from members, who can point to their work on Stack Overflow as a kind of portfolio.

“We’ve always thought that if you can get a group of experts together there are business opportunities around that where everyone can benefit,” Spolsky said, who will be sharing more about the career site on the upcoming Launch conference.

Spolsky believes the emergence of good question and answer sites can also help combat the rise of content farms. Stack Overflow recently announced it would partner with search engine Blekko to use its community of users to help improve programming- and tech-related searches. But Spolsky believes Stack Overflow can also replace a lot of the spammy content with expert-driven answers.

“This is the next thing,” he said. “After search and social, it’s questions and answers.”

Related GigaOM Pro content (sub req’d):