Another case: confused questions which ask several different things at once, most or all of which are already answered.
Often this attracts replies which cover one aspect. Or, it attracts big omnibus answers which are hard to vote on (because they may cover one aspect better or worse). The end result is a Q/A which just clutters the site. Future visitors who wonder about some portion of the question end up with a lot to wade through. Basically this is the failure of bb-style discussion forums for Q&A, brought here.
I have been voting to close these as duplicates of the primary question and adding links to other questions. But I guess I could also be convinced that Not A Real Question, Too Localized, or Not Constructive would be better, maybe often with a suggestion that Chat is a good place to take a wide range of topics.