I've had knots thrown back at me by my planer before. That was before I upgraded to the DW735 with those power feeders and a much deeper body to keep the cutters further away from the human, though.
I have a reasonably safe checklist and set practice for my jointer and I still don't trust the thing.
I don't remember hearing about any serious planer injuries (though I'm sure it happens), jointers on the other hand are more ornery than an alligator with all them teeth and no toothbrush.