Herd mentality can be a beautiful thing (when relating to a herd). Everyone is safer from predators, there is harmony, and everyone seems socially satisfied. Life is generally easier for an active and engaged member of the herd.
However, when humans develop a herd mentality and start saying, thinking, and doing the same things creativity is often diluted, innovation is compromised, and distinctiveness is lost. The dangerous thing that people need to be aware of is how easy it is to join the herd. Quitting the herd mentality takes a little work, but can be quite fulfilling.