The main thing they got right is that pages on the Stack Exchange network include (as primary content) exactly one question, followed by the answers to that question. That's it. All other side discussion, requests for more info, expressions of gratitude, etc, are secondarily attached as comments. They are visually and conceptually separate.
In retrospect, this is totally, obviously what you want, but there was a lot of momentum behind making Q&A sites look like a forum.
This really varies per site. For example, since StackOverflow is primarily for concrete technical questions, overly subjective discussion questions are liable to get moved or closed; however, if you're interested in something concrete but still broad (e.g. how to use existential types), you're likely to be fine.
On programmers, on the other hand, most of the questions involve a good bit of discussion; the majority have several answers. This is because the focus of the site is different.
Finally, I think there's a lot of selection bias--you're more likely to remember closed questions, and the sort of questions that get shared on HN are the sort that don't really fit in StackOverflow.
On a mostly technical note, you're most likely seeing closed questions, not locked ones.
Locking prevents discussion, answering, or any other actions by anyone except one of the 12 moderators; there are currently 16 locked questions on the site.
Closing, on the other hand, can be undone by any five of the 7500+ users who have 3000 reputation.
StackOverflow is not a site dedicated to hosting discussions on "interesting" topics. It is a site dedicated to getting the highest quality answers to technical questions. And it does that marvelously. As a byproduct it also fosters the sort of community that ends up providing interesting discussion from time to time, but if the site became about that it would not last and it could easily cause a derailing of the site's main purpose.
Just because something is "good" doesn't mean that it belongs on SO.com.
The main thing they got right is listening to the community. Meta sites were great, users can suggest changes, question existing rules and stuff and it got StackExchange to where it is, Listening to community = growing community.
If you ever want to understand "social" not as in the buzzword but as in "what's it really about" I can highly recommend the Stack Exchange podcasts.
I know this is not their aim but it's actually one of the most insightful podcasts about social networks out there. So many great insights simply stemming from the conversations they have. For instance the one with Chris Poole from 4chan.
I'm 90% sure that 15M of those new users are just Jon Skeet clones that upvote him!
But in all seriousness, stackexchange have completely stolen the parade from all other community driven Q&A sites.
Joel was correct when he withdraw support for customer hosted Stack sites, and went through the incubation process.
Stackoverflow has totally wiped out all of the other failing programming websites, and the community is a great one to be apart of. (I hated those sites that would obfuscate all the answers and try and get you to pay to sign up, while cloaking everything on Google).
Whenever I'm stumped and turn to google with a programming question, it's always such a relief to see SO as the top result. No other site has the same quality of answers, IMO.
I certainly don't miss wading through all those crap Experts Exchange links in the Google results (actually the advice on that site was often pretty good, but the business model was repellant).
Weird part was that though the answers were obfuscated, all you had to do was to scroll down the page and get the answers - what a joke! But the answers were good.
It took us a while to convince EE to change its strategy, but with some help from a giant Panda, EE has been convinced to implement a "Freemium" model at the end of the month when it launches a completely rebuilt site.
I'd love for non-programming sites like http://diy.stackexchange.com/ to catch on. I feel a little queasy every my most relevant search leads me to Yahoo Answers.
One of the things I love about StackOverflow is that I learn even when I'm the one answering the questions. People are always happy to point out how I can make my code more clear, idiomatic or elegant all without trying to belittle me. Not to say other communities are worse--it's just that the absolute level of quality at SO is very good.
And, of course, since it's basically an MMORPG, it's addictive. Not that I mind--one of the best ways to learn a technology at an intermediate level is answering questions there. It's much more productive than a real MMORPG and more convenient time-wise than just learning from a book or by having a project (of course, I use those too: all the different methods augment each other).
I decided to learn ruby on rails (via http://ruby.railstutorial.org/ I highly recommend it) and stackexchange.com has been an invaluable resource. Both as I learn the ruby language, and troubleshoot issues as I'm coding.
When I want to learn a new technology, I start following a tag and silently lurk for a while and then start answering to the questions. I have been able to learn so much by answering question on SO.
Those guys wouldn't buy into it. It seemed liked such an obvious solution to the existing solution. Walking down an email thread then getting to the end with no answer. I think it's especially useful for a new or esoteric technology because it allows new users to come up to speed quicker. Scala, Go, Haskell can be learned in short order.
The one thing that could be improved is to partition answers that become dated. Also, some questions could be asked every 3-5 years. For example, best frameworks, etc. Tech changes fast.
Did anyone else notice that the page uses custom-made buttons for all platforms other than G+? I wonder if those buttons were made with not allowing Twitter and Facebook to track users in mind.
Joel, Curious about your opinion on HN culture vs. SE culture in the context of growth. Both sites saw significant growth in 2011, but from my perspective, HN culture has been far more affected than SE. If you agree, do you attribute this to something specific that you are doing at Stack Exchange and is there something you would do differently to improve things here?
Some people discussed the situation on HN earlier today[1], but I think you bring a unique and valuable perspective to the issue. I have my own theory (i.e. SE has a superior technical solution for reputation)[2], but you have some of the most directly relevant experience.
I think that's the prettiest page I've ever seen on their network. Hopefully we'll see some creative/design refreshes this year -- it makes a big difference.
If you look at some of the newer sites, they're generally prettier than the original trilogy sites. Still have the same basic design and still all about the text of questions and answers.
I love the simple design of the main sites - SO, SU and SF. Keeps the question and the answers as the central focus. Things don't have to be pretty just for the sake of it.
I was probably responsible for 100k of those views as I was learning Rails. Cool note: I put a question on stack, went to do a Google search seconds later, and my question (I just made) came up. Cray
Have they published any revenue numbers? I'm happy to hear that they're growing like crazy, but knowing that they'll still be around in a couple of years would be even more awesome.
In retrospect, this is totally, obviously what you want, but there was a lot of momentum behind making Q&A sites look like a forum.
In other words, their success is well-deserved.