I cannot think of any specific personal references where i have virally marketed a product or service, however i have on many occasions posted a status about a product or service that i have really enjoyed. Also i have promoted status’ about events that i am attending and their locations so they other could join along in the fun.
Viral Marketing is very effective for certain products, because when things go viral. Millions of people see them, and then they tell all of their friends. This creates the link for eveyone and usually millions of people see the product.