Transmission pattern of chain letters:

The final result was a "tree" of nodes and connections that was long and thin, not one that funneled out as in the case of rapidly spreading information. Gossip in smaller communities may fan out quickly, but – as the new study shows – such a pattern changes with scale. This large-scale spreading of information is a rare case, since most circulated e-mail messages never reach such a large number of recipients.

"A natural assumption going into this study was that information would spread explosively, reaching many people in only a few steps," said Liben-Nowell and Kleinberg. "Instead, a much more complex picture emerges, with the chain letter following longer, narrower paths. After this initial surprise, we eventually found possible ways to reconcile the deep, narrow structures we observed with the facts we knew about human social networks."