internet forums

I've noticed that when people reply to old threads in various forums, they are often admonished or ridiculed for doing so. For example, today I read a useful reply to a 3-year old thread, but someone subsequently responded to it with "Zombie Thread Alert!"

It's true that the person who originally created the thread or who originally asked the question, probably no longer needs the answer or information provided. However, those answers can be quite useful to other people like me, who are having the same problem/question, and who have found the thread through a search engine.