As professional sports go, the NFL stands out for two distinct reasons: its exceedingly popular, and its extraordinarily brutal. Just last week, for the 30th straight year, pro football was ranked the favorite sport of American adults by a massive margin. And the NFL is a money-making behemoth, attracting a growing number of fans to live games and raking in nearly $10 billion in revenue in 2012. Until, that is, you remember the risks, and the sometimes tragic repercussions: several NFL players have in recent years taken their own lives, with autopsies revealing brain damage consistent with routine hits to the head;