[canistr]

Twitter and Youtube, sure.

But the blast radius of a Facebook post doesn't have the same reach given the majority of posts go to your explicit network of connections. Unless you're specifically referring to Facebook Groups? But then are we certain it's different from Reddit or other forums?

[itake]

Facebook Groups and Pages create ways for people to share content, triggering exponential growth (e.g. user shares meme to their page so that their friends see it. Their friends choose to re-share. wash. rinse. repeat.)