Daniel Kahneman argued that independent sources of information and
ideas are important to good decision-making.
James Surowiecki popularized this idea in his book, The Wisdom of
Crowds.
This title is a reference to Charles Mackay's Extraordinary
Popular Delusions and the Madness of Crowds.
However, people get information from other people, and especially
today in the age of social networks on the Internet, they tend
to evaluate the quality (utility and reliability) of information
based on the source.
In the reading from David Easley and Jon Kleinberg's Networks,
Crowds, and Markets: Reasoning about a Highly Connected World, we
see an extreme example of an information cascade. This is when
after a few "information dominos" topple, they all fall in the same
direction -- they're not independent.