In it, he demonstrated that the weakest, not the strongest, social ties are the most irreplaceable ones. Since then, his weak tie theory has been validated repeatedly by more recent, data-driven research.
The finding, in fact, is not as counter-intuitive as it first appears. If you surround yourself only with people, views and connections that are close to you, then you will inevitably form a clique. The problem with cliques, as Tim Harford observes in his sociocultural study Messy, is that they become blinkered: "In a clique, everyone knows everyone and all tell you the same. The more peripheral the contact, the more likely she is to tell you something you didn't know."
What we don't know, of course, is precisely the thing we need to master in order to progress and flourish. Denying ourselves access to it, avoiding weak ties, is strategic folly. This has been illustrated emphatically in politics of late. The failure of the two opposition parties in the last general election was, to some extent at least, their failure to be peripheral. Neither of their leadership teams managed to reach meaningfully beyond their electoral cores. They spoke to their strong rather than weak links. A friend of mine drove across America just prior to Trump's election victory and, a devoted Democrat, ended his trip convinced that Trump would win. The periphery between the two coastlines gave him the insight of the weak tie.
As we know from Dominic Cummings' recruitment blog, politics and communications are inextricably linked. So, with the new decade unfolding before us, I would urge adland to run towards the periphery, to nurture and cultivate the weaker links it has perhaps neglected over the past decade, particularly during those late teenage years.