<p>I doubt we really need canonical threads on different subject matter for data.  It might be helpful to have canonical threads on different data types (binomial vs. normal), but not the meaning behind the numbers (e.g., presence of headache vs. not, presence of gastric distress vs. not, etc.).  That seems to me like it negates the need for a canonical stock market thread.  I'm not saying it should be off limits, but I mostly don't think it makes sense.  In particular, the follow-up question, "What would it address?" seems like a major warning sign.  </p>

<p>In the specific case of the stock market (or generalize to include other investment options, such as bonds, commodities, forex, etc.), I do see some value in a short thread that explains <a href="https://math.stackexchange.com/q/433831">the principle of no arbitrage</a>, simply because there is no escaping the occasional ignorant question.  However, we arguably already have that: <a href="https://stats.stackexchange.com/q/21395/">What machine learning algorithm can be used to predict the stock market?</a>  </p>

<p>On the other hand, if there were a type of question, say about neural networks, that is contextualized in the stock market and pops up commonly, but is always poorly asked, then a canonical thread on that issue would be helpful.  Moreover, it would probably be most helpful to use the stock market as the example situation to motivate the question.  I don't follow either investing or these types of questions on CV well enough to provide a great example, but something like modeling / forecasting a mean when the error variance changes unpredictably might be a the sort of thing where it would be helpful.  </p>
