Why do 'some examples' and 'list of things' questions get closed?

Question

A common form of question that is often asked is the "what are some examples of..." While this is hinted at in the help center

Please make sure that your question is not too broad, or strongly rooted in opinions. We should be able to answer your questions in the equivalent of a few pages of text and graphics and provide references to support claims. If you have questions that warrant an extended discussion, feel free to come to chat.

explained in those links, and written about in meta site for all of Stack Exchange in the list-questions tag, these questions show up often enough that it merits asking again here.

Why do these list questions get closed and down voted on Programmers.SE?

Answer 1

There is no right answer.

The simple and most important answer in realizing why these questions get closed is "there is no right answer." And before people get too hung up on "but there are right answers" the key to that sentence is the answer not answers. There should be a singular answer to the question that is complete and correct rather than a dozen answers that are all right and only complete when all read together.

Lacking a right answer, everyone has another example to add to the list. "What are some (real world) examples of ${concept}" can get an answer from each person who reads the question and has used that concept. "What ${book|blog|tutorial} should I read on ${topic}?" likewise has a constantly appending possible answer no matter how constrained the topic is.

Some of our common list questions have a standard close reason that tries to get to the heart of the problem with lists:

Questions about what language, technology, or project one should take up next are off topic on Programmers, as they can only attract subjective opinions for answers. There are too many individual factors behind the question to create answers that will have lasting value. You may be able to get help in The Whiteboard, our chat room.

Quality of answers

The unfortunate bit about list answers is that there is an ever diminishing quality to the answers. Sure, you can sometimes get someone posting a good answer out at answer number 24, but each answer tends to be lower quality than the previous one.

This is likely because one doesn't feel the need to restate everything that was said before.

Stack Exchange's founding goal

Stack Overflow was founded because it was too hard to find good material in forums. In particular, you had to go through many posts to get to the answer and often the follow-up posts spill off on to tangents and discussions making it harder and harder to find the answer.

Thus, Stack Overflow (and all of Stack Exchange) was designed to make it easy to find the answer (sorting by votes, accepted answer to the top) and at the same time close questions that are going to be endless discussions.

The core problem with these questions in a Web 2.0 world is that they don't generate good content. They may be interesting for an instant but really fail when it comes to long term maintainability and quality of content. The lack of quality content often discourages the very people who you want to have that generate the quality content.

This was seen back in the days of Usenet and repeated again and again in forums and mailing lists. The quality of the material inevitably falls to the lowest quality that is accepted. People who want to read or provide the higher quality material ultimately go and find another place to contribute.

While it is certainly interesting and there are people who enjoy contributing and reading the lists, Stack Exchange wants and needs to retain the people who are going to give the thought out quality answers. Thus, the bike shed questions and lists become aggressively moderated - closed and deleted in order to try to maintain the expected quality of the material asked and answered and thus retain the user base that is providing in depth answers to hard problems.

A frequent objection to this aggressive moderation is that "this is where the experts / knowledgeable community is - I won't get as good answers elsewhere." The important realization that should be had is that it is because of this focus on answerable questions (rather than lists and bike sheds) and allowing the questions that generate the lower quality content ultimately pushes these people away.

This is not to say that these questions are not interesting or important to their asker (and I will admit to going to other sites to read them) - it's just that structure of the site that Stack Exchange provides needs keep its focus on quality answerable questions that have definitive answers rather than never ending discussions and lists of other examples. It is through this that Stack Exchange remains the place that people come to to get the answers to the hard questions (rather than going to Yahoo Answers).

Where to ask these questions

That really depends on the question that you are asking. As mentioned in the close reason, chat is one place where people can ask discussion and list style questions. Other sites, include Quora and Reddit which do a good job of providing anecdotes and discussion. Specifically within Reddit, there are entire subreddits that focus on one particular type of list question (/r/programming can be thought of as an endless "what programming blogs should I read" question).

Many of the experts that are here, don't constrain themselves to being here only. Eric Lippert of C# fame can be found on reddit too. There are other eminent names of programming that are active in multiple communities that cater to specific types of questions and discourse. And yes, you will likely find that the standards of quality for other sites are different than they are here as each site is trying for a different slice of that Web 2.0 pie.