[John_KZ]

They have to choose one of the two, publish their decision, and act accordingly.

Honestly the real problem is that they pose as a raw communications medium while they are definitely not one. Facebook has political, cultural and financial interests according to which they filter your communications. Even if they say "we alter your data stream" somewhere in their ULA, they are still dishonest as they do it in a way that convinces you thay the effect is small while in fact it is not.

One more consideration: editorialized newspapers are fine, because all readers get the same paper and and work out the bias. If the bias is extreme or blatant lies are circulated, public discourse will lead to consequences for the publisher. With facebook, filtering is so pervasive, elegant and fleeting that you can't tell what's done on purpose and what isn't (a design goal imho).

So I'd say that even if Facebook publicly declared itself to be a heavily edutorialized publisher, without a way to know the bias, they shouldn't be allowed to operate on a personalized content basis, because unless they publish their feed algorithm and a way to verify it works as it's supposed to, there's no way to know if they are acting maliciously.