I like the answer entitled "Why We're not a Forum""Why We're not a Forum". Having said that, I want to call attention to a particular kind of question that is somewhere between objective and subjective. I'm referring to design questions. There are numerous design questions that come up, concerning the design of object oriented systems, or the design of software packages, or the design of relational databases.
These questions are somewhere in the twilight zone. At first glance, they seem like the kind of straightforward Q&A that SE seems to handle well. And the asker usually wants an answer he or she can use, not an extended discussion.
Here's the problem. For every non trivial design case, there is more than one satisfactory answer. And which answer is "best" depends on the particular use case, and on what criterion is being used for "goodness". It's usually some kind of trade-off. So what ought to be a straight up Q&A turns into a discussion. Or the question gets closed before that can happen.
But most of us don't want to declare design questions out of bounds, even including those of us who very much want to avoid turning SE into just another forum community. This is not a simple problem, IMO.