I would guess more injuries occur during regular plays because there are more of them during the course of a game. The
more serious and life threatening injuries are more likely to occur on kickoffs though. Kevin Everett of the Bills was very
close to being a quadriplegic the rest of his life after attempting a tackle on a kickoff against the Broncos a few years ago.
IIRC, the NFL changed the rules on kickoffs shortly afterwards. Receiving teams were no longer allowed to form a multiple
man wedge in front of the return man. The kicking team would would counter by having a man called a wedge buster. His only
responsibilty was to throw his body into the wedge and risking life and limb doing so. The new rule eliminated the need for
the wedge buster.
Personally, I think it's a bad idea proposed by Goodell. No matter how much you tinker with the rules,football will always
be a violent sport. I'd hate to see the day come where players like Devin Hester,Darren Sproles and other great return
men are taken out of the game completely.