The JoinShield.com ask you to complete a few training tasks. In this they've used images and video from the upcoming movie "Thor". In one of the task you have to figure out who's lying, and one of the women says "I'm not a Life Model Decoy, I don't even know what that is"
So what can this mean? Could Marvel have S.H.I.E.L.D be developing LMD's in they're future movies? I guess we wont find out until these movies get on screen!