Hewlett Packard’s social networks research. Includes study of an online community and an information flow model.
Unlike viruses, which spread indiscriminately from host to host, pieces
of information are propagated by people who find them interesting and
who pass the information to others who they think may be interested.
Since people are most similar to their immediate contacts, and this
similarity decays as the distance in the social network between
individuals increases, information becomes less relevant further away
from the source and is unlikely to spread throughout the network.