Many people are.
In fact, referral marketing is exactly what is working for the Internet right now. If an organization is able to create a compelling product or service which enables an outbound email component, then the consumer will likely buy it, then refer two friends, who refer two friends and so on. It spreads like a disease, like a virus. When customers are excited about your product, they'll do the work for you. Initially, in order to get them excited, you need to think about offering them something that would be directly relevant to them, that better serves them, making them feel special.