In a "tipping" model, each node in a social network, representing an
individual, adopts a behavior if a certain number of his incoming neighbors
previously held that property. A key problem for viral marketers is to
determine an initial "seed" set in a network such that if given a property then
the entire network adopts the behavior. Here we introduce a method for quickly
finding seed sets that scales to very large networks. Our approach finds a set
of nodes that guarantees spreading to the entire network under the tipping
model. After experimentally evaluating 31 real-world networks, we found that
our approach often finds such sets that are several orders of magnitude smaller
than the population size. Our approach also scales well - on a Friendster
social network consisting of 5.6 million nodes and 28 million edges we found a
seed sets in under 3.6 hours. We also find that highly clustered local
neighborhoods and dense network-wide community structure together suppress the
ability of a trend to spread under the tipping model