http://spectrum.ieee.org/automaton/robotics/aerial-robots/every-quadrotor-needs-this-amazing-failsafe-software

Oh this is awesome! It is for fear of exactly this that ive always stuck to hex' and above.

I was not too long ago flying my hex over a crowd of about 15000 people capturing aerial footage for a minister friend of mine in Hyderabad while he was campaigning, one of the motors just went dead but I still managed to bring it down safely, ofcourse, the term safely is debatable, well lets just say at the time my only concern was not to let it crash into anyone so instead I quickly maneuvered it into a tree at the side, does that count for bring it down safely .

Great bit of info, thanks for the share Anwar.