Okay guys, lets not get bent out of shape towards each other... deep breath time... *inhaaaaaaale* 6 seconds *exhaaaaaaale* okay lets move on..
My concern with this feature is it might turn into a DoD situation where most of your nades would come flying back at you. I used to see it all the time... soldiers would simply walk up to and quickly throw them back... which we can all agree wouldnt be happening... ever, in reality.
What happens then is people get sick of their nades coming back, so they learn to cook them perfectly, which, as you can imagine, leads to other complaints.
The only way I could see something like this working without being abused would be to activate the ability to pick up a live grenade and throw it ONLY IF YOU ARE PRONE, that is to say you wouldnt have the ability to do so in a crouched or standing position, that way if one lands next to your face, you can throw it away (which doesnt mean it wont blow up in your hand, you just never know, lol).
... but even then I could imagine people, if the distance was close enough, running and diving on nades just to throw them back, so I dont know how that would actually play out.