Here is one instance where the "related posts" algorithm's results (while often magic!) weren't great.
A user just asked this question:
Use Jquery to create a CSV Download
Of course, it's a quadruplicate and has a great original here - with 18 upvotes, and a top answer with 56 upvotes:
Export to csv in jQuery
However, I couldn't really admonish the OP for not looking at the "Questions that may already have your answer" section, because it doesn't show up there. In fact, most suggestions aren't even jQuery related! (The 1st result is the question the OP just created, so that doesn't count.)
It would be really cool if it could.