They say raising venture capital is a young man's game. Joel Spolsky is a very logical exception to that rule and will announce today that his question and answer site for computer programmers, StackOverflow, has raised $6 million from some of the hottest investors in Web technology. Union Square Ventures, Ron Conway, Chris Dixon, Caterina Fake, Joshua Schachter and others have put in money. Industry luminaries Clay Shirky and Anil Dash have joined the team as advisors. That's a real dream team for a Web startup.

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Spolsky is the author of the cult-classic blog Joel on Software, he's been the CEO of bug-tracking software maker Fog Creek Software and at 45 years old, he'd never raised venture capital before. Now, in a mere 18 months, he and a small team have built a red-hot website that sees over 7 million unique visitors monthly and is ready to take its formula outside of the computer industry.

StackOverflow is a simple concept: People post technical questions about computer programming, other people post answers, and then users of the site vote the best answers to the top of each page. Reputation is accrued over time as your answers get voted on, and programmers on both sides of the questions love the service. Some advertising and a job-posting service based on the reputation programmers have built up by answering questions on the site have made StackOverflow profitable for months.

Fast, free, high-quality answers to technical programming questions is something there was substantial demand for. The market leader for years has been a site called Experts-Exchange, a fee- or performance-based service founded in 1996 and the favorite target for StackOverflow's rhetorical slams. In 2008, Spolsky and Jeff Atwood, a widely respected developer in his own right, founded StackOverflow, named after the technical phenomenon wherein too much memory is used by the data stack storing data about active subroutines.

The site came out of closed beta in September 2008 (we covered it first among general interest tech blogs). Then it hit 3 million unique visitors just 4 months after launching. In October 2009 the company announced Stack Exchange, a service that offered white-labeled installations of the StackOverflow software for use by anyone else. In December, Stack Exchange was selected by Google to power the Android Developer support forums. The site is thoroughly cool. For example, it periodically offers data dumps of all its user data in aggregate, under a Creative Commons license, for outside analysis of the social dynamics between users and more.

Plans for the Future

It's generally acknowledged that the Stack Exchange vision of white labeling for anyone didn't work. Spolsky says that very few communities really picked up enough steam and the licensing fee meant that a community had to be lead by someone who was both capable of managing the community and of monetizing it, two criteria that whittled down the number of candidates quickly. (See MathOverflow for an example of a really good, super-nerdy niche site that did work, though.)

Now Spolsky says the plan is for the company to launch a handful of very targeted sites running the same software but focused on offering objective answers to technical questions in other verticals. The StackOverflow community has a running vote on what the first sites will be about, and leading ideas include statistics and data visualization, GIS, mathematics, search engine optimization, home repair and the care of firearms.

Spolsky says that future sites will be rolled out through an automated process wherein a number of people will propose a site, then debate the ground-rules for content on the site and then gather a core group of experts to commit to the site. Once an algorithm has determined that a critical mass has been built on a topic, then a new site will open up on StackOverflow's own servers.

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How will those sites be monetized? Spolsky says now that the company has money in the bank, he doesn't have to worry about that for a good long time. His backers support the "get big first, then figure it out" strategy for monetization. StackOverflow, for example, couldn't have built its job finding service if it didn't have data about the qualifications of 7 million programmers. The same or different business models will emerge as the new sites grow in size, he says.

Spolsky says that programmers have joined StackOverflow because it's a lot like blogging, but with a lower barrier to entry. Busy professionals join the site and share their knowledge for the joy of sharing it, and because they benefit from the collective wisdom offered there. He believes that there are a good number of other fields where there are objective answers to technical questions and where people care more about the right answer than they do about what their friends have to say about something. Spolsky says the much-hyped Quora is a nice competitor but has a different, more social vision - and a long way to catch up to StackOverflow's 7 million monthly uniques.

Spolsky says the decision to raise money and assemble the top-shelf team that he has was motived by the realization that StackOverflow is an unusual opportunity. "It's very rare, but we saw an opportunity to get big fast," he told us by phone. "We're not going to have to worry about the cost of servers, hiring a few people, getting office space. Before I would have walked around New York for weeks looking at all the office space to save $2k/month. We don't have to be careful anymore. We have the confidence to blow this out on a worldwide basis. We're a top 700 site on the Web today; we want to be a top 70 site."

He says he didn't expect to be out raising money, but the type of business StackOverflow became - and the opportunities that backers offered - made it a clear choice. "I've always been against the concept [of raising money]," he told us. "For the vast majority of businesses, it just doesn't make sense. There are a very limited number of opportunities in which VC makes sense, and I didn't expect to be in one of them, but suddenly StackOverflow revealed itself to be one of them."

Spolsky says that the easiest way he's heard people explain the difference between StackOverflow and old fashioned forums is that when you go to StackOverflow, the right answer is at the top of the page. That's a charming way to put it and it's sure to be interesting to see the team that's assembled take a shot at building that kind of experience around other kinds of topics.