Eminem used a massacre/mass occur wordplay the same way I did a few years ago on his Rap God track.
http://www.letsbeef.com/battle_detai...n=tb&id=277803 Chances he actually went on this site and saw it are next to none though.
There are a finite amount of punches/wordplay combinations that can be made so coincidences are bound to happen. But then again what's stopping up and coming artists with a lot of hype from doing it? What copyright laws do the artists on here even have on their side when it comes to text battles?