Patience, my friends. Free attracts eyeballs. Give away something, sell something. Viruses only spread when they're easy to transmit. Viral marketing works famously on the Internet because instant communication has become so easy and inexpensive.
Digital format make copying simple.
From a marketing standpoint, you must simplify your marketing message so it can be transmitted easily and without degradation. Short is better. The message is compelling, compressed, and copied at the bottom of every free e-mail message. Scales easily from small to very large To spread like wildfire the transmission method must be rapidly scalable from small to very large. The weakness of the Hotmail model is that a free e-mail service requires its own mailservers to transmit the message.