The principle behind Stack Overflow (and Stack Exchange by extension) is to be that first search result on Google. So the mere ability to find information on Google/Wikipedia/Wookiepedia is not necessarily a black mark against a question. That, I'll grant you.
But I'll expand on what I said in the elevator pitch. The key word here is "trivial" and yes, that word does have an objective meaning. In order for a question to be more than mere trivia, it has to require one of two things:
Some education, training, or experience that makes a person uniquely qualified to answer; or
A certain degree of research, i.e. interpreting or applying publicly-available information.
Any site based on fiction - including SF.SE - is really going to struggle with point #1. There's nothing to study or practice in the context of passively-consumed entertainment. But #2 is possible, and in fact, serious SF fanatics love to pore over scripts and scenes trying to fill plot holes and try to unravel the mysteries of the author's universe. That's what being a fan really means. If that doesn't interest someone, then they are a passive consumer and don't need or deserve an exchange for it.
Trivia is actually one of the more common reasons that SF (and fantasy and other fiction) forums and groups die out. While serious fans are trying to make sense of all the ret-cons and make sure their fan fictions are actually consistent with canon sources, the bottom-feeders are wasting time with stupid trivia games. "When was Q's first appearance on TNG?" Who cares?
It's not so much that the questions are terrible by themselves, it's just that there are endless permutations of them and not a single one of them - not a one - actually adds any value to the site or community, because somebody could just as easily find the answer somewhere else within 5 seconds.
The criteria for "trivia" is really actually rather simple on a site like this:
The question can be answered from a single source - either reference or canon;
The source provides a direct answer, not requiring the viewer/reader to extrapolate or connect dots; in other words, there is no obfuscation of the answer, deliberate or accidental;
The source provides a clear and simple answer, not requiring any in-depth analysis of its own in order to understand.
That's basically it. It's very easy to grok. But just to be sure, I'll put it another way, from the perspective of the person asking the question. Ask yourself, am I asking this question because:
I've read all the books / watched all the episodes, and just cannot put together all the clues? or
I just can't remember and don't have the time or inclination to look it up myself?
In fact, I can dumb it down even more than that:
- Does this question help me, or other fans, gain a deeper appreciation for the work? Or, is it just idle curiosity?
I see people complaining that some here want to restrict this site to trivia questions. But nothing could be further from the truth; keeping the trivia off a site like this is where the value will come from. The "sci-fi forum" concept has been done to death. Hell, there are conventions for it. The only thing I can think of that would set this site apart from all the others is thought-provoking questions.
So yes, "trivially answerable" should be a benchmark, but with proper definition around the word trivially. If somebody has to cite multiple sources, interpret the (pseudo) scientific claims, or decipher clues left by the author, then that's not trivially answerable. If posting a single link to Memory Alpha definitively answers the question, that is trivial, and such questions shouldn't be here or on any other SE.