When an off-the-cuff 'I bet' becomes a real wager.
When a shoving match escalates to knives and guns.
When sporting event breaks out into a brawl.
When a political party uses its power to destroy its opponents.
When the Enemy pits himself against Christ Jesus.
In each of the examples above the game ceases to be a game and becomes a life and death contest.
WinnerTakeAll is the most serious form of Playing For Keeps.