There are plenty of resources that "define" good questions, e.g. every site's FAQ, here and here. The heuristic seems to be that good questions correlate with good answers.
That does not seem to be true in all cases. For instance, a (scientifically) interesting question -- that is one that has a good answer which might be unknown -- can be "hijacked" just because (for instance) it is near topics that invite for battles of opinion, causing lots of "bad" answers to be given. This has arguably happened to varying degrees in several questions:
- Can a dynamic language like Ruby/Python reach C/C++ like performance?
- Why has research on genetic algorithms slowed?
- Why are there so many programming languages?
Two questions naturally arise:
- What constitutes a good answer?
- What to do with bad (=not good) answers?
For reference, check out these guidelines on Skeptics Stack Exchange.