Its a big problem. On the one hand social media companies are utterly unsuitable for the role of arbitrers of truth. All they do is enforce the fashionable, safe truths, which might end up not being safe or true. On the other hand there is definitely disinformation out there, carefully crafted to achieve specific goals. We need a sort of peer review for social media, some sort of trust network that you can use to assess the reliability of information. The fact check is one such mechanism, though who checks the checkers is still a issue..