MIAMI - As America's most popular sport encounters a liability problem . . . gladiator Junior Seau kills himself with a shotgun blast to the chest and leaves his damaged brain to study . . . as awareness and penalties increase around an NFL commissioner confronting the oxymoronic task of making a violent game safe . . . and as the rules change but the culture really doesn't . . . we think we know this forever-growing monster we are cheering on Sundays. But we don't. We have no earthly idea.