I demoed XCOM to the board-gaming group at the library. When the Commander was allowed to access Emergency Funds, he took them all. That round, the Chief Scientist and the Central Officer spent below capacity, and the Squad Leader fully deployed. Even so, there was a budget surplus, and the Commander spent it all on Soldiers and Interceptors. Next round, everyone spent heavily. During budget payout, there was a eight-credit deficit: enough to take the least-panicked continent into the orange, losing us the game.
And that's how unlimited defense spending can cost you the planet.