In the Middle Ages, the attention of peasants was focused on events that occurred within an area bounded by a day’s worth of walking or riding a horse. During the industrial era, peoples’ worlds have been multiplied by the quantity and accessibility of mass media, especially television and advertising. Today, people are drowned in a daily tsunami of more-or-less validated information, advertising pop-ups of recommendations from Amazon, suggestions provided by the search engines of Google, buzz, spam, rumors and social networking (chapter 5, no 9).

So people do not know where to turn for solid useful information. In an information society that produces too much information, our lives feel more and more atomized.

Attention is not elastic. It quickly reaches its limit, and the limit(s) have different levels :

This is the time of available attention from the human brain. The flow of knowledge is proportional to the attention multiplied by time.
According to Davenport & Beck.

Here is an American model of this attention economy :

To operate effectively this model examines three levels of users :