In my own experience ~7/10 times the duplicate question is something entirely different and I have to spend longer searching because of someone's ignorant pedantry.
IIRC this happened while other users seemed to be happily karma farming best-of questions.
I haven't seen so many lately but I've decided to start making bookmarks on them and here is one I found a few days ago: https://stackoverflow.com/questions/13202705/what-are-the-us...
Myself I've witnessed first hand a question about networking being shot down on networking because it was between company networks instead of inside company networks.