That's true, short blocks of wood are not a good idea, I remember as a teenager I was sent out with a guy to drag brush for him to chip. Towards the end of a long day as I was bringing over one of the last piles I saw him pick up a small stub block 4-5" x 5" long, he tossed it in and like a cannon it shot back out and got him right in the crotch, I fell down right where I stood because I was laughing so hard, in fact I probably added a half hour to the job cause I just couldn't stop laughing.
I'm pretty sure that was the last time he did that though.