Quoted from Marten:
Does it damage the machine or do you think people get to play for too long if they can do this?
I think if it doesn't set off the (slam)tilt it can't be very violent.
The Pinball 101 DVD I think outlined(with maybe a DW?) the damage that can be done with bangbacks. Screw holes get elongated, etc.
For (non bb)death saves, still the legendary one to me was in the PAPA video for Iron Man. RIght outlane drain and the the guy nudges the whole cab in a J-shape, and only gets a warning.