How are social memory complexes created?

[Billy]

"A mind/body/spirit social complex becomes a social memory complex when its entire group of entities are of one orientation or seeking."

This is what I don't get. So a social memory complex will comprise of every person on the planet right? If that's the case, then does that mean only a small percentage of the current population will eventually 'make it'. I guess I'm trying to understand what will be going on throughout this transition period. Is it already known roughly which people will be inducted into earths smc?