Groupthink - Is it a real problem?

Recently over coffee, a friend and I were discussing real and imaginary problems and "Groupthink" came up.

Googled definition - Groupthink is a phenomenon that occurs when a group of individuals reaches a consensus without critical reasoning or evaluation of the consequences or alternatives.

When does this occur?

1. When a team or org has too many people with the same socio-economic-ethnic background trying solve world problems; The classic silicon valley problem where a bunch of white males try to solve problems without any real understanding of the problems they have personally never faced.
2. When you hire people from the same education institutions/ education background because they are "highly-ranked". Their view of the world maybe colored by the views of their professors/teachers and the training they receive.
3. When you hire too many people from the same Organization and they all have "been there and done that" and are here to do it quickly and usher in change.

Does any of this sound familiar or resonate with you? I would think when you work for a multi billion dollar MNC, there would be checks and balances to ensure that there is diversity of thought. That the "system" would ensure balance and ensure that talent does not over-index from any one of the above mentioned cohorts.

Consequences

Pressure to deliver quick results in today's environment results in people taking the easy route. Long term success is sacrificed for short term gains. Solutions that are brought about miss the context when you try to replicate what you have done before elsewhere. There are just too many extraneous factors that impact us today and "Context is King" and the folks trying to replicate what they have done before often miss this. This leads to sub optimal problem solving, increased cycle times and a myriad of bad decisions brought about by a lack of understanding.

A side effect of hiring homogenous talent is the creation of The "In-crowd" and "the rest" - Its human nature to be drawn towards people with similar backgrounds and groups that self select are nothing new. Groups may form based on language affiliation, ethnicity, alumni of a company or college. Leaders need to ensure that everyone/ every idea is treated equally on merit. If that's not the case, how are "the rest" supposed to counter a leader who actively bats for the "in crowd" because of a familiarity bias in "the way we think". This ultimately results in those who feel left out, leaving after realizing they are pushing a rock up a hill and they would rather spend their energies somewhere where they are recognized for what they do and not which cohort they belong to.

Is this line of thinking naive and idealistic? What do you think? What's your example of corporate group-think? Is the problem "Real" or "Imaginary"?