Once they got into the business of curating the newsfeed rather than simply treating it as a timeline, they put themselves in the position of mediating what people are going to see. They became a gatekeeper and a guide.
Media in the Age of Algorithms
Tim O'Reilly

Thank you for an even-handed and typically insightful analysis of this long standing but suddenly fraught issue.

You appear to have skirted the core issue with some pretty circumlocutions, “curating,” “mediating,” “gatekeeper” and “guide,” but the actual words that invoke the responsibility (and cost) competitors and those who care for the unwary desire, are “editing” and “editor.”

Perhaps you avoided that terminology deliberately, as it might appear you are making the same legacy perspective error that others are making in your view.

But Facebook is not editing or an editor, the selections are made by the user.

Yes they are.

Facebook is merely responding to instructions, implicit and otherwise, from the endpoint. This isn’t the long cycle mass transmission/publication model over scarce channels we associate with editors and their appropriate responsibilities. It is gossip on a massive scale, with instantaneous full duplex communication between each individual user and the algorithm.

It’s arguable that the intent of the algorithm is Facebook’s to determine, still, caveat emptor. I believe Facebook is that kind of network that can carry arguments to its own despite, if any care to use it to enhance the vulnerables’ understanding.

We know that Facebook is trainable. Robert Scoble gives lessons on how and “I Liked Everything I Saw on Facebook for Two Days. Here’s What It Did to Me” is a cautionary tale.

Thus I believe Facebook has not crossed the editorial Rubicon, and is not subject to the noblesse oblige of saving credulous boobs from their willingness to embrace that which they already believe.

If this abdication of responsibility leads to loss of custom, that's the audience’s right and responsibility. Many channels and ease of entry mean competition, sans the network effects, is always a threat. More of a threat than the hair on fire outbursts from, to be frank, those whose hopes were not met in the election.

I don’t share the view that success of social media imposes an obligation to behave like some IRL “town square.”

There are always risks in a free press and free speech, in the land of the free and the home of the brave I expected better understanding of that than this.

Thanks too to Matt Cutts, for the reminder that “You get what you measure.” It was novel to me.