This question has for aim to help reducing the number of unanswered questions.
Looking to the unanswered questions I went through this question called Error typesetting large bracket with multiple lines. Actually the problem was just that the
amsmath package was not loaded, and had nothing to do with the error mentioned in the question.
There wasn't a real conceptual/theoretical TeX-related problem here, so what should be done with this question, and more generally with all the questions presenting the same kind of problem due to something not at all mentioned in the question and not really useful for other users? I would say that knowing that someone forgot to load a package does not improve the general use of TeX and so may not really deserve an answer which will remain on TeX.SX...
What do you think? What do you suggest to do for these questions (I already saw other questions presenting the same problem but I am not able to find them just now)?