I am wondering about this remark in general. When I looked at the link it is something that I don't understand the tie in to viral marketing.
Viral marketing is using techniques that cause an idea or product to spread easily. Viral marketing tools are email campaigns, you tube videos, twitter etc. Anything that can be picked up and passed on is how I think of viral marketing. Put one thing out - and it is picked up and spread on by others along the line.