2010 was an absolutely amazing year here at Stack Overflow. We grew from 7 million visitors to over 16 million, putting us in Quantcast's top 400. We raised $6 million in venture capital, and we went from three full time employees to 27. We built a 7500 square foot office in New York, and we launched a ton of new features and sites, like Stack Exchange, a network of 33 Q&A; sites on diverse topics from cooking to computer science. Stack Exchange grew 51% in December alone. Wow. The expert Q&A; model that Stack Overflow pioneered is really working. The statistic I'm proudest of is the percentage of questions that get a good answer, over 80% (and many of the new Stack Exchange sites have 100% answer rates!)
Traffic
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.
Traffic to Stack Overflow grew 131% in 2010, to 16.6 million global monthly uniques. Uniques are counted by cookies, so the number of human beings is less. We also measure the number of page views (top level pages loaded, which doesn't count images and supporting files), which has similarly grown from 31.8 million per month to 72.8 million per month, i.e. 129% growth. Based on the number of people who do come up to us in hotel lobbies, we're pretty sure that ALL the programmers in the world use Stack Overflow. (Source: completely made up. But seriously, when was the last time you met a programmer who didn't use "El Stack"?) In order to keep growing and making the Internet more awesome, we have to expand into new subject areas, like Molecular Biology and Harley Davidson Belt Buckles. That's what Stack Exchange is all about. Stack Exchange growth is insane. In six short months, we've gone from zero to 1.5 million monthly visitors, growing 51% in December.
If, as planned, we continue growing at 51% a month, we will be bigger than Facebook in 15 months. We're ALREADY bigger than ocn.ne.jp (No, I've never heard of that either. But we're bigger). Jeff and I are already planning who will play us in the Aaron Sorkin movie. (Tyler Labine and Zac Efron, obviously.) Now, obviously, all this TRAFFIC isn't worth a thing if people aren't getting answers to their questions. That's why our favorite thing to measure is "percent of questions answered." And not just any answer will do, either: to count a question as "answered", either the original poster has to accept the answer, or a third party has to upvote the answer. This is where Stack Overflow really shines compared to other Q&A; sites: we actually get questions answered. Three of our sites actually have 100% answer rates!
New Sites
Last summer, we relaunched Stack Exchange as a democratically-driven network of sites on topics chosen by our users. Some of these sites are directly related to programming (for example, Game Development), but some are quite far afield, from English Language to Cooking.
We call it the Stack Exchange network, and at StackExchange.com you'll find a directory of all of them, along with some hot questions, statistics, leaderboards, and other tools so that you can follow the sites and tags that you're interested in. We learned a long time ago that the only way to get questions answered promptly is to have a critical mass of knowledgeable users, so we have an onerous process called Area 51 where sites are proposed, discussed, and voted on. If a proposed site doesn't have critical mass, we just won't create it. Even if it does get created, it has to maintain a certain level of traffic and quality or we'll close it down. So far, 13 sites have gone all the way through the Area 51 process and launched. Dozens more are already in beta. Hundreds more are in active discussion and will launch when they reach a critical mass of interested participants. The development team has been knocking out new features at a constant pace. They built an amazing web-based chat system, and we've added literally hundreds of new features and improvements to the core Stack Overflow engine which we roll out continuously.
The Company
At the beginning of the year, Stack Overflow LLC was just three developers working from home. In the spring, we raised $6 million in venture capital from Union Square Ventures and a long list of celebrity angel investors, which allowed us to expand rapidly. We hired a team of great people, including several of the high-reputation users that you know from Stack Overflow.
We now have community managers, a sales team, two full time system administrators, and Very Important Administrative Overhead like myself, but most importantly, we have a great team of developers, in New York and around the world, building the next generation of cool features, like the important "wheel of blame" feature, which we can run at any time to calculate precisely who is responsible for anything that went wrong. (Contrary to popular belief, it's not always Jason Punyon.) To make room for all these people, or, at least, those who live in New York, we rented a 7500 square foot, class A, super-elite batcave in New York and then fixed it up to be nice, with cool furniture including Aeron chairs and height-adjustable desks, and lots of glass to bring views and daylight deep into the batcave. And of course, we have private offices with a half dozen gigantic 453-inch monitors for each developer. And there's an amazingly cool Star Trek couch. Does your company have a Star Trek Couch? I didn't think so. We also have Rovio, a little robot that our remote developers can use to visit the office "virtually." (There. I said "virtually." Are you happy now?)
Overall 2010 has been a real breakout year for Stack Overflow, which is now the largest programmer website in the world (source: me) and the best, fastest-growing Q&A; website in the world (source: also me). We've got an incredible team firing on all cylinders, so we're really looking forward to 2011.