The biggest problem I tend to hit nowadays with Stack Overflow (and other Stack Exchange sites) is when someone says that while doing $X they ran into problem $Y and want help with $Y, and none of the answers tell how to do $Y. They all say that for doing $X a better approach is to do $Z instead of $Y.

That's great for the person who asked the question, because presumably doing $X that they actually care about.

But I'm not there because I'm doing $X. I'm doing something totally different that does actually need $Y.

I've had times where I've found a dozen different SO questions asking about how to do $Y and ever damned answer to every damned one of them was a "you don't need $Y for what you are doing...do this instead" answer.