Beginner question on "Pull is mostly evil"

During my initial self-education I came across the maxim "don't pull, fetch+merge instead" and have been doing that.  I think I followed most of the "pull is (mostly) evil" discussion but one facet still puzzles me: the idea that pull will do a merge "in the wrong direction" sometimes.

Do I understand correctly that this occurs only in the presence of multiple remotes? Can someone provide a simple example of a situation where pull would do the "wrong" thing?

Thanks