I did this recently when a blog post described the exact, very niche issue I was having with a production server. This post described the symptoms of the issue clearly and included a flow-chart of required fixes. There was no preamble, just clear guidance. It was more an incident management manual than a blog post, and it saved me a lot of Googling under considerable stress.

I sent the author a quick thank you, explaining how it helped me in my hour of need. Exactly as others have said here, it goes a long way to making the effort of blogging worthwhile!