Tonight, Lee's iPad questioned him with a blue pop-up window: "Do you want to buy one Chest of Gems for $99.99?"

Lee could use those gems to immediately fortify his army. He tapped "Yes," almost without thinking. In less than a month of playing around two hours a day, he'd spent nearly a thousand dollars.

Game developers have a word for players like Lee: whales.

These Guys' $5K Spending Sprees Keep Your Games Free to Play [Wired, via Twitter]