One problem related to battery dead has been reported for the 2012 Volkswagen Jetta. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2012 Volkswagen Jetta based on all problems reported for the 2012 Jetta.
Key got stuck in the ignition with motor running. Could not turn to "off" position. Although I could kill the motor by releasing the clutch (manual transmission), I still could not turn the key off and, therefore, would have to just let the battery die after many hours of sitting there with the key on. I could not leave the vehicle unattended as anyone could have gotten in, started it right up, and left with it. Did a google search and found that opinion placed the blame on a faulty ignition switch. Also discovered many others with this exact same problem who had to have their ignition switches replaced, so this is a known problem with Volkswagen.