As crazy as it might sounds, the manufacturer believes that there is a real risk to some Legacy, Impreza & Outback models produced between 2010 and 2013.
Unfortunately for any ghost hunters out there getting excited about this it's not linked to any paranormal activity, and is in fact related to models which contain an automatic transmission and a remote engine starter. Official line from Subaru is "If the the remote engine starter is dropped, it may malfunction and randomly transmit an engine start request without pressing the button".
It may sound daft having a car randomly start however there are more serious risks associated with it if the car does decide to take on a life of its own. Once again the official line from Subaru states that "The engine may inadvertently start and run for up to 15 minutes. The engine may then continue to start and stop until the fob battery is depleted, or until the vehicle runs out of fuel. If the vehicle is parked in an enclosed area, there is a risk of carbon monoxide build-up which may cause asphyxiation" - Crazy stuff!
Thankfully the defect only seems to effect cars sold in the US, so anyone this side of the Atlantic is safe....for now!