The other day when I went to play test the Rebellion Beta, I unwittingly set myself up to create a game where it was not possible to achieve victory.

I set up Twin Empires map with one ally and 6 enemies in 4 teams, 2 per team.  I also had not set team victory to yes, but did set teams to lock.  When I eliminated all other factions, my computer ally dropped all the pacts we had together, but could not become an enemy (due to team lock) but neither could win (due to no team victory).  So I had to simply exit the game in a stalemate of my own creation.