This is a waste of your time for certain questions, though. The ones ending in "urgent please help" just scream that the poster is going to wait 15 minutes, briefly scan the answer sections for code snippets, and move on.
If it's a public, indexed forum, I'd say answering is not a waste of time. Someone can use a search engine and find good answers years after the original question was posted.
That's exactly it – SO has become a list of everyones problems ever, with solutions. I frequently find answers to things I need to know on SO, sometimes years after the person asked.
