People post puzzle or contest problems, without making any attempt to solve them (simply copying the original question). These questions get upvoted - not because the OP did a good job, but because the original source is good.
Examples (all copied verbatim from a contest, with no attempt at solving the problem):
The answers are very interesting and I like reading both questions and answers.
Should such questions be converted to community wiki by moderators instantly, when they are first seen?