The problem is twofold: Operating systems that don't penalize apps for being resource hogs, and browsers that allow any tab but the frontmost one to consume sig

The problem is twofold: Operating systems that don't penalize apps for being resource hogs, and browsers that allow any tab but the frontmost one to consume significant amounts of CPU or memory. In other words, no Javascript program should be allowed to DOS your machine. It's within the power of the browser and the OS to restrict this; they just choose not to.