DARPA Project to create bio-engineered creatures that will live indefinitely -- what could possibly go wrong with a plan like that?

According to Wired.com the Defense Department’s advanced research arm is launching a project to develop a designer organism with cells built to not break down over time. They plan to build in DNA making the organism loyal to us, and preventing an enemy from subverting it to their use. And as a fail-safe, they will include a genetic kill switch—a molecule known only to us that will instantly shut the organism down should it run amok. Given what we know about the predictability of events at the quantum level, what could possibly go wrong with this plan?