The main reason guerrilla marketing took off was its incredible effectiveness at breaking through our advertising blinders. Advertising executives are under a lot of pressure to make their campaigns successful. At some point, it occurred to some ad people that they could make ads so irresistible that they would actually be passed around willingly by customers. Guerrilla marketing sometimes takes the form of a viral campaign. The viral campaign happens organically and spontaneously; if it’s pushed too hard by its creators there’s a pretty good chance it’ll never get off the ground. Some of the most successful guerrilla marketing campaigns have taken the form of viral videos or websites.
Here are some excellent examples of guerilla marketing:




Here is also an excellent video with some great examples of guerilla marketing:
http://www.youtube.com/watch?v=QlBMF1MvAGY