At least in the case of the "opposite of 'déjà vu'" question, I'm not sure how the person asking the question could research the question effectively. If I were to try to answer it, I suppose that I would start by running a Google search online for 'déjà vu' + 'opposite' and see what came up—but "opposite of X" questions are very tricky to provide a groundwork for, and I think they depend more on there being someone in the EL&U community who happens to know the requested term already than on directed research by someone who doesn't. This is by way of suggesting that some questions can be interesting and worth posting here despite not being especially researchable.
The "What is the etymology of the word "bae"?" question is different. A modest research effort by the questioner would surely have turned up at least a little of the information that Josh61 provides in his useful answer. Nevertheless, I voted to leave that question open, essentially because I thought that the question was good to have on EL&U. There is a great difference in baseline effort between the "bae" question as it was formulated and Hugo's compact but well-researched question from last December, What does “fleek” mean and when was it first used? And yet I think both questions should be on the site—and I'm glad that (for the moment, anyway) both of them are.
A wide-ranging site dedicated to English language and usage strengthens its authoritativeness by dealing with subjects of wide popular interest, and I think that questions about the meaning and origin of very popular slang terms fall squarely into that category—especially because they are too new to have been examined in a systematic way by most general-reference sources. So if such an inquiry into "bae" is ultimately appropriate for EL&U, and if having a thorough and timely response to the question is valuable to the site, it seems counterproductive to me to reject a question that poses the issue squarely and concisely, on the grounds that the person asking it didn't do—or didn't detail having done—any significant research into the question.
Because this is a question-and-answer site, it's easy to get caught up in the sense that the questions asked here are one-offs from particular individuals who owe the site and prospective answerers at least a threshold level of effort in order to qualify for participation. But the vast majority of people who benefit from EL&U's content are drive-by visitors who haven't done a stroke of work beyond typing, say, ""bae: etymology" into a Google search window. When they do that and find a link to the "bae" question and Josh61's answer at EL&U, it doesn't matter to them or to the site's prestige and usefulness that the person who asked the original question didn't undertake a preliminary investigation of the question. All that matters is the factual and stylistic quality of the answer.
To me, a lack of effort on the questioner's part becomes annoying when the question involves a truly general-reference issue that the questioner didn't bother to look up in an obvious source. But the underlying problems in that case are that the question isn't interesting beyond a simple look-up level and that the questioner could have avoided cluttering EL&U with such simple stuff by doing the work him- or herself. I certainly wouldn't be any happier with a questioner who did the research, found the relevant answer in the general-reference work, and then came here—citation at the ready—to ask whether the information was correct.
I suspect that close-voters have gravitated toward the "insufficient effort" close reason because it offers a convenient way to discard questions that are weak and uninteresting for other reasons—chief among them, being too elementary, too localized, or too narrow in applicability to be of use to other site visitors. But the trouble with using one reason to close questions that are in themselves unsatisfactory for another reason is that the nominal reason for closing takes on a life of its own. After all, if the reason you give for closing a bad question is that the questioner seems not to have done any (or adequate) preliminary research, doesn't it follow, as a matter of procedural due process, that you should also close good questions that don't show any research effort?
Ultimately, I think, a person's attitude toward objectively interesting questions goes a long way toward determining how that person feels about closing questions for "insufficient effort." A substantial number of voters at EL&U see questions as applications for inclusion on the site: If the question doesn't measure up for any reason—including failure to demonstrate preliminary research effort—it should not be accepted. Eventually, if the question is good, someone will ask it in an acceptable way, without compromising the site's standards for asking a question. By definition, a question that fails to satisfy the threshold criteria cannot be a "good question." In the meantime, the fact that no active entry on EL&U addresses the subject of the question is simply a non-issue.
On the other hand, a person who (like me) imagines that the long-term goal of EL&U is to be a place where visitors can find answers to every possible interesting, non-general-reference, factual (as opposed to opinion-based) question about English may take the view that good questions justify themselves. From my perspective, rejecting an interesting question because the person who asked it didn't adequately research it first is a bit like disqualifying a question because the person who asked it didn't have an advanced university degree: the qualification may well bear on the fitness and quality of the questioner's questions in general, but an interesting question is an asset to the site regardless of how fortuitous its origin may have been.
So, yes, my preference would be to accept any "interesting" question on its merit as a question, and to reject any bad question (by which I mean a question that is of little interest to anyone but the questioner, or a question whose answer is readily findable in a general reference, or a question that is so open-ended or dependent on opinion that it defies practical answering) on its lack of merit as a relevant question for this site, rather than on the basis of its asker's evident lack of research effort.
