Under "Four things to design for" in A Group...

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4.) And, finally, you have to find a way to spare the group from scale. Scale alone kills conversations, because conversations require dense two-way conversations. In conversational contexts, Metcalfe's law is a drag. The fact that the amount of two-way connections you have to support goes up with the square of the users means that the density of conversation falls off very fast as the system scales even a little bit. You have to have some way to let users hang onto the less is more pattern, in order to keep associated with one another.

This is an inverse value to scale question. Think about your Rolodex. A thousand contacts, maybe 150 people you can call friends, 30 people you can call close friends, two or three people you'd donate a kidney to. The value is inverse to the size of the group. And you have to find some way to protect the group within the context of those effects.

Sometimes you can do soft forking. Live Journal does the best soft forking of any software I've ever seen, where the concepts of "you" and "your group" are pretty much intertwingled. The average size of a Live Journal group is about a dozen people. And the median size is around five.

But each user is a little bit connected to other such clusters, through their friends, and so while the clusters are real, they're not completely bounded -- there's a soft overlap which means that though most users participate in small groups, most of the half-million LiveJournal users are connected to one another through some short chain.

IRC channels and mailing lists are self-moderating with scale, because as the signal to noise ratio gets worse, people start to drop off, until it gets better, so people join, and so it gets worse. You get these sort of oscillating patterns. But it's self-correcting.

And then my favorite pattern is from MetaFilter, which is: When we start seeing effects of scale, we shut off the new user page. "Someone mentions us in the press and how great we are? Bye!" That's a way of raising the bar, that's creating a threshold of participation. And anyone who bookmarks that page and says "You know, I really want to be in there; maybe I'll go back later," that's the kind of user MeFi wants to have.

You have to find some way to protect your own users from scale. This doesn't mean the scale of the whole system can't grow. But you can't try to make the system large by taking individual conversations and blowing them up like a balloon; human interaction, many to many interaction, doesn't blow up like a balloon. It either dissipates, or turns into broadcast, or collapses. So plan for dealing with scale in advance, because it's going to happen anyway.

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Stack Overflow had one of its principles that you could find things easily - right there on the top of the answers. However, with opinions, everyone has them. Furthermore, people vote on how much they like the opinion rather than how useful it is. This means that:

1. You're going to have lots of posts. Consider "What is the single most influential book every programmer should read? " - https://stackoverflow.com/questions/1711/ . It has 214 answers. How many of those are duplicates? How much of that is noise? That question was locked in 2012, consider how much more there would be there today... and how much less useful it will be as you go through it.

2. Curation becomes difficult. The value proposition of Stack Overflow is that its curated (by the community). As such questions grow, they become more and more difficult to curate.

3. There is no "right" answer. The answer you are looking for has just as much of a chance of showing up on the last page than the first.

4. The discussions that happen around opinions - Stack Overflow intentionally made discussions hard to have (see the Group quote above). Consider how often you find the answer to a technical code problem by searching Google and finding Quora or Reddit as the top result.

There are better formats for providing opinions and polling a group. Whats more, many of the people who are providing answers are there because it doesn't allow that format of question. There are many other sites that do (and encourage) that niche of Q&A - Stack Overflow doesn't need to fill the role of every type of Q&A.

One of the Stack Exchange sites has "Why was my question closed or down voted?" with an answer that links to several other resources https://softwareengineering.meta.stackexchange.com/a/6491