“Bonding social capital constitutes a kind of sociological superglue, whereas bridging social capital provides a sociological WD-40. Bonding social capital, by creating strong in-group loyalty, may also create strong out-group antagonism, [...].”

Putnam deems bridging social capital more important for social connectedness than bonding social capital. He seeks a breadth of connections, which cause society and government to function well. They oil the wheels, as does WD-40. Bonding social capital is beneficial too if not taken to an extreme.

“On the contrary, American history carefully examined is a story of ups and downs in civic engagement, not just downs – a story of collapse and of renewal.”

Putnam is documenting the decline of civic engagement in the late 20th century for the purpose of beginning a public conversation about how to reinvigorate it. He does not maintain that the erosion of social capital and the ensuing negative consequences are permanent.

“Financial capital – the wherewithal for mass marketing – has steadily replaced social capital – that is, grassroots citizen networks – as the coin of the realm.”

Putnam is referring to political participation, which became capital-, rather than labor-, intensive in the late 20th century. Candidates relied upon mass advertising to reach voters instead of campaign volunteers going door-to-door. The effect was to turn active citizens into passive spectators.