I suspect a secret alliance, or possibly a multi with the following:
Newbs
chessmyantidrug
They seem to play numerous games together, never attack each other, and leave massive open borders between each other.
Take a look at game 620185. Between turns 6 and 11, no armies were placed on Columbia by chessmyantidrug and only 1 was placed on Panama by Newbs.
Other games these two have shared are: 617302, 599062 and 668533. Other players in those games seem to have suspected something was fishy, as well.
I filled out a support ticket but have no idea how long it takes for the admins to get to those.
Any thoughts?