We played our second game yesterday. One player who was well behind committed intentional suicide so as to become a slave of the leader. We later worked out that was impossible - he moved into the desert which was uninhabitable - the rules state you can't migrate into an uninhabitable hex.
However, you could move next to another player's unti so as to exceed your footprint and therefore starve to death.
Some of us thought it was clever (he was losing), some of us thought it was exploiting a loophole in the rules.