[xab31]

Even middle schoolers are taught that there are "reliable sources" and "unreliable sources". Wikipedia (pretty good usually) is not considered a reliable source, let alone Twitter or Facebook.

Even a reliable source, like an academic article or a nationally syndicated newspaper, can be wrong, and are, frequently. Basic logic and rationality would be enough for people to realize that "I saw it on Facebook" has basically no informational value.

If anything, therefore it is the "reliable" sources which should be fact-checked, since they have greater credibility and influence, and because no one with any sense would believe something just because they saw it on Facebook and Twitter.

The fact that many people appear to do so says, to me, that when people are on Facebook and Twitter, they really don't care about the truth of the matter, they are looking for things to fit their confirmation bias. Therefore we would expect "fact checking" on such platforms to accomplish very little, except for irritating people who are semi-consciously already aware that they are consuming right-wing propaganda, and see left-leaning propaganda as informationally equivalent, just a product for a different audience.