Really? I assume all 20,000 people aren't close personal friends.

I work at a company that's an order of magnitude bigger, and I interact with about 5 people on a daily basis and maybe know the names of about 20 people there. (We have a big building, so the team I'm on mostly has the floor to itself.)

I am sure there is groupthink among the 5 of us, but I'm not sure that there's an opportunity for us to think like the other 280,000 people. If we do, it's a coincidence.

No more so than a small start-up with your friends. Groupthink has far more to do with the work environment than the size of the group.

Especially with uniforms like that!