The spread and spread of this viral content depends on both strong and weak links in the network. Strong ties help build trust between people so they can rely on each other and build ideas and make plans together. Many of the examples presented so far in this book have relied on strong ties, in which individuals find each other, identify with common ideals, and thus receive better information and support. But if you only rely on strong links, that means information will only stay in circles who know it well. Weak links form when people on the fringe also touch new information—such as seeing a post or photo on Facebook or Snapchat.

Without strong connections, there company banner design will be no consensus and no community can be formed. But without weak links, new and unusual ideas cannot spread. Change's viral campaign on behalf of Leo didn't take long. Every time someone signs up on that site, the policy maker or decision maker targeted by the petition receives an email notification. Take Leo's petition, which asks Maryland's governor to support legislation still under consideration in the state that would prevent SNCF and its subsidiaries from bidding until compensation is paid. Today, the Change website launches about 20,000 new petitions every month.

A quick glance at the site reveals that some petitions on narrower local issues can be effective with only a few dozen signatures; petitions on large national or international events are Thousands of people signed up. Part of what makes petitions on Change’s website so effective is that they act like spotlights, bringing the spotlight to a key person, an issue, and a specific request. The speed, scale, and efficiency with which the web is reaching individuals, accumulating signatures, targeting people to send emails, are of course key elements that make this process work so effectively. Anything of this sort would have required months of door-to-door pleas, spending money on envelopes and postage.