Herd mentality describes how people are influenced by their peers to adopt certain behaviours, follow trends, and/or purchase itemsSource:Wikipedia Let me point out to you some well knows examples of Herd Mentality
Greed is an excessive desire to possess wealth or goods with the intention to keep it for one's self.Source:Wikipedia Greed is totally opposite of fear. Here the tendency is to hoard and not share your knowledge or possessions with the world. Greed also is tendency to make short term gains as a replacement to gains in the future. Tendency of being greedy to make money in short amount of time caused immense havoc in the history. Dotcom boom, mortgage crisis and booms and further recessions are big examples .