I recently read an article stating that the support in most front seats were inadequate in the even of a rear end collision. The pins that stop the seat from going back into the space of a potential rear seat passenger are put in place to help prevent injury to rear seat passengers.
There are lawsuits involving just about all the big manufacturers because someone got rear ended, the impact of the collision cause the front seat back to collapse into the back seat, and the back seat passenger was severely injured and/or killed.
Those pins that someone drilled out are what prevents this issue. The seat back can't go back very far when the back seat is so close. I posted a link below if anyone wants to read about it.
http://www.cbsnews.com/news/seat-bac...-nhtsa-action/