Perhaps this site should not have been allowed into beta. Take a look at the list of example on-topic questions on Area51.
Are there any inventions that were accurately predicted in science fiction? If so, what were they?
Oddly, this question is still open, even though questions of the same nature (e.g. FTL methods) and with more definite answers are being closed. In meta, it seems like infinite list questions like this are considered not acceptable.
Would warp travel be possible sometime in the future? Or is it impossible?
I think this would be considered ok (but I couldn't find any example of a similar question already posted). Probably some people would "subjective" close vote it, and others would try and give answers that showed what current technology is doing and how it might relate.
I like scientific accuracy, which hard science fiction writer would you recommend and why?
This would be closed.
What science fiction novels have well developed alien languages?
This exact question was closed.
In the Dune series, why are they not using computers and programming related technologies?
This was asked and is presumably acceptable.
So of the "five great example questions" we have one or two that are actually allowed on the site. If the people that defined and committed to the site don't know what is acceptable and what isn't, then how do we proceed?
Perhaps we could go back to the Area51 site and see if there are any set of five questions that would be on-topic, and we could post those somewhere for people to use as a reference.
I decided to go ahead and do this. I looked through the list of all example questions on Area51 that were voted as on-topic: I ignored those that have already been clearly deemed off-topic (lists of indefinite length, recommendations, identification), and those that have either been already asked or had an extremely similar question asked. For the remaining ones, I thought of a question (that I honestly wanted answered) that was the same sort of question, and asked it. Based on what happens to these questions, that may provide some more guidance.