[Illuminated One]

Scorched earth -> you (my invader) are not going to win -> someone else has to win -> for maximum effect the person in the lead is going to get everything I have left in the lab...
Furthering the lead the leading player is not exactly more fair than just going AI.


Anyway talking about fair or balanced (see vfb's point) or when you can't do anything makes little sense imo.
Especially in the situation that A feels like there's nothing he can do (and therefore a sub isn't found easily) it's only a conflict between three player interests.
Player A: I can't win this war so I can as well give up.
Player B: Hahaha, all these territories without resistance. It's really sad to see you leave A.
Player C: Keep playing A. You don't have to play to win. But if you stop now B will secure such a huge lead I can't win anymore. You completely ruin the game. Why should I keep playing if I can't win?


All I'd say is that it is more fun to play against human than against AI, and in that spirit I'll try to get a sub when I go out in future games.
I wont commit myself to finishing a game where I've nothing left to do, or that I find hard to handle, though.
I'll also refrain from attacks on staling neighbours unless I'm driving his invasion army out or he has freespawn.