If you are talking about using GM led factions, some players might suspect fowl play on the part of the devs if their island was the one to lose. Lame and inconsiderate as it may be. Of course, something completely automated could work (increasing the spawn rates for undead and monsters) could work but lacks the fun story element of the typical invasion.
What do you mean, "their island"?
As far as I know, devs play on every continent.
