From BarCamp DC Wiki
The word-of-mouth discussion outlined the differences between
word-of-mouth marketing and
viral-marketing and examples of both. It was generally agreed that viral-marketing has a more grass-roots origin while word-of-mouth marketing usually implies a marketing scheme that intentially targets individuals with
social network potential, for example, the
Word-of-Mouth Marketing Association and
Tremor. An good example of viral-marketing is the "job-ad" video by Connected Ventures ‘
Lip Dub - Flagpole Sitta by Harvey Danger’ that was viewed 1,089,248 times in four months.