Not necessarily.
Starship Troopers.
This only happens because a human being's short lifespan, limited mind, and constricted point of view mans that a human's perceived self-interest is very limited in scope. A planetary scale hive mind could have a much longer lifespan and a (literally) inherently more global view.
Externalities arise because of a limited scope of knowledge, and persist because of self-interests of tiny scope. We think markets are so wonderful, because the distributed computational power of many individuals can keep up with global complexity. What if a single hive mind could command the same number of neurons, without the disparate competing self interests getting in the way?