As I've participated in this site I've seen quite a few questions whose answer will always be, "It depends."
I think that all answers should give a justification for their opinion. Answers like this seem not helpful at all, since they don't give an opinion, much less a justification for that opinion.
Anyone have suggestions for giving constructive answers on this kind of question?
You can't go wrong with what you know from your experience.
If you can think of things that'll cause the answer to change, preface your answer with that you're assuming. An even better answer would provide multiple versions of the answer with different assumptions (i.e., "If X is Y and Z is A, this is right, otherwise that is right").
A lot of times questions that elicit "it depends" answers aren't very good questions to begin with: narrowing down the focus of a question so it actually demands a non-wishy-washy response is a hard thing to do for a lot of people. If you think you can improve the question, you should either by commenting or editing. Otherwise, the question really should be closed.
In terms of other people answering with non-answers, downvote them without pity, or remorse, or fear and if you are so inclined, leave a comment as to why. "It depends" doesn't help anyone. We all know it depends, that's why the question was asked in the first place.
Remember SE sites are an economy - this is exactly what down votes are for. If you believe an answer is unhelpful, show it.
[Edit] Ironically, I probably should have posted this as a comment instead, since that wasn't exactly what your question was about.
Indeed, this is covered in Good Subjective, Bad Subjective which is linked in the faq and every question closed as "not constructive", as well.
http://blog.stackoverflow.com/2010/09/good-subjective-bad-subjective/
Great subjective questions invite sharing experiences over opinions.
Certainly experiences inform opinions, but the best subjective questions unabashedly and unashamedly prioritize sharing actual experiences over random opinions. It’s more useful to share with us what you’ve done than what you think. Everyone has an opinon. It takes zero effort or imagination to have an opinion about anything and everything. But people who have done things, real things in the world, and have the scars and arrows in their back to show for it — now that’s worth sharing. You should be uniquely qualified to have your opinion based on the specific experiences you had. And you should share those experiences, and more specifically what you learned from your experiences, with us!
and
Great subjective questions insist that opinion be backed up with facts and references.
Opinion isn’t all bad, so long as it’s backed up with something other than “because I’m an expert”, or “because I said so”, or “just because”. Use your specific experiences to back up your opinions, as above, or point to some research you’ve done on the web or elsewhere that provides evidence to support your claims. We like you. We want to believe you. But like wikipedia itself, {{citation needed}}. And good subjective questions make this clear from the outset: back it up!
