The "something" you refer to, is the problem of scale. Within a "small, local information bubble", you have enough experience with each source of information t

The "something" you refer to, is the problem of scale. Within a "small, local information bubble", you have enough experience with each source of information to be able to accurately evaluate its reliability. Some in your hunter/gatherer group were reliable, others were not, you knew who was which. With a large group, at some point you can no longer tell, because each source is a one-time source (or close to it). Plus, the potential profits from compromising that source become so large that, for example, newspapers get bought by corporations, to help mold popular opinion. People cannot tell who they can trust, but they know there's a lot of untrustworthy out there. So, they retreat back into a local bubble. Whoever is in this person's local bubble, is currently getting a valuable data point as to their trustworthiness. :)