That didn't get disseminated and diffused to tens of millions. If something was published they'd look for official sources or corroborating sources and or secondary evidence. If AP, EFE, UPI, Kyodo, Interfax etc all get their news from one source [Twitter] that's just laziness.

“ A lie can travel halfway around the world before the truth can get its boots on” has been a cliche for a hundred years. I don’t think internet social networks are a difference in kind, but they probably are a difference in degree.

Agreed but I said "apart from scale and reach". The point I was trying to make was that people have always found it fairly easy to believe non-credible sources. In this sense, social media is not qualitatively different. Only quantitatively different.

A large quantitative change is indistinguishable from a qualitative change: what's the difference between light rain and a flood, between some small waves and a tsunami?

What I meant, is that in the eyes/ears of those RECEIVING the information (and believing it uncritically), there's no difference. People have always had a predisposition to uncritically accepting information from those "in the tribe", whether that be extended family, or an internet echo chamber. Presumably this was a survival optimisation. Trust those "close", and distrust "others".

“My dad's co-worker's, girlfriend's uncle works at ... and said...” doesn’t reach the whole world instantaneously

It does now.

the scale and reach