Yes, very much so - long, gradual built-up of momentum by interested parties is typical to grassroots movements. It happens slowly - and then all at once.

It's more like a "stand alone complex" from the Ghost in the Shell entertainment series.

>"a stand alone complex is multiple copies of a behavior, object, view, ect, existing without an original."

It doesn't imply there wasn't an original, but usually that original was just the seed crystal for the behavior.

The "flash" part of flash mob describes the execution of the mob, not the planning. It could be planned years in advanced and still be a flash mob if their audience didn't expect it.