This works both ways too. More than once, I've looked at a supposedly urgent post, and done a fair bit of research, and/or written and tested code and posted it, along with some explanation, and the OP is never seen again.
+1, or they carry on totally ignoring your post.
I fess up to having got more terse lately, I've taken to not posting now rather than say what I'd like to.
I have seen this from the other side as well, I'm on other forums in areas that I'm not experienced in and I've occasionally got responses like
"Just add ABC to the XYZ"
And I think "WTF is ABC and XYZ?"
Rob