I have been noticing some questions that appear (to me at least) to ask questions of the type in the title, and I was wondering, if absent any "hard" facts, such a question is allowed?
Examples is something like this.
This is one of those cases where the validity of a question is determined by the answers it receives.
That being said, anyone with common sense should be able to judge if their question can be answered by hard facts. From the FAQ, we only want to deal with practical, answerable questions based on actual problems that you face. The question you linked to was only going to lead to opinionated responses, the merits of which would not depend on facts.
If you asked a question like "Is a solid-state drive better then a hard drive?", yes you can answer such a question with hard facts, and you can also deliver an answer that could recommend which type of technology a user goes with in the end (depending on his or her needs). You also don't need to be opinionated in your answer, since you can provide details comparing both without out-right saying "yes SSDs are better for everything!!!!1111one".
My point is, while you might not need to have hard facts explicitly stated in the question, if it's not possible to answer the question without some kind of proof or hard fact(s), the question will surely be closed.
Also, for that question you linked to, I quote:
What do other people have now? Any preference over one unit versus a modem and separate wireless router? Any suggestions on brand and model? I am in Boulder, CO and am getting Comcast internet.
You can see the clause here - is there truly any difference between a seperate modem/router, or an all-in-one unit? Most likely not, and I don't think debating that on SU would benefit the community whatsoever. Also, from the FAQ, this is not a place to find a shopping or buying recommendation. If someone wants to find a product, they should do some research (reviews, benchmarks etc...) and decide for themselves.