Response is the key to communication. Communication goes on. It is the continuation of the intellectual and emotional exchange.
Sometimes, we find that some people don't just respond. Lack of response is lack of humanity. Lack of response is a message you don't value the relationship. Lack of response is insensitivity. Be human. Respond.
Sometimes, people ask us for help and favours but we don't wish to oblige. So, we avoid responding. This is not correct. Respond and say you can't do it explaining the reason or not.
A response indicates care, and compassion. It means you value what the other person has said and hence you respond.
Lack of response is a slap on the face. But don't be hurt. Only ego hurts. When someone does not respond, don't feel the pain, because some people are just insensitive. It's not your fault, it's theirs. Then why lose sleep over it ?
Show you care. Don't hurt someone. Because it will come back at you. It's karma. Respond to everyone.