What does Pariser mean when he says we've moved from human gatekeepers to algorithmic gatekeepers on controlling the flow of information? Why is this a problem?

The use of phrases, fragments, and punctuation can influence the mood of a passage; keeping this in mind, how would you describe the mood of the followingpassage? "fog on the essex marshes, fog on the kentish heights, fog creeping into the cabooses of collier-brigs; fog lying out on the yards, and hovering in the riggingof great ships; fog drooping on the gunwales of barges and small boats. fog in the eyes and throats of ancient greenwich pensioners, wheezing by thefiresides of their wards; fog in the stem and bowl of the afternoon pipe of the wrathful skipper; fog cruelly pinching the toes and fingers of his shivering little'prentice boy on deck." (5 points)