I grew up playing football into highschool. I love the game and have an 11 year old son. He's never played because he's never wanted to, but I'm now of the opinion that I wouldn't let him play if he were to change his mind. IMO, football has been evolving for the last 2 decades and we're starting to see the results. Richard Dent and Junior Seau are 2 very sad and compelling examples of that.
6'4", 260lb linebackers that run a 4.6 forty are not supposed to exist. 20 years ago, they didn't exist. Now, the league is chock full of them. I believe the hits are getting harder from highschool on up and we're starting to see the toll that it is taking (especially in regards to head injuries). When my dad played highschool football, you goofed off for nearly 10 months of the year and then played football once the season rolled around. As soon as it was over, you went back to goofing off. When I played highschool football, you had summer conditioning, 7-on-7 passing camps, the season itself, and then a football conditioning class for the rest of the year that counted as a PE credit. Obviously, building these athletes only gets more intense as you get into the college and pro levels.
As much as I love football, I firmly believe the athletes that are being produced from highschool on up are out-pacing the ability to protect players. In fact, there probably isn't a way to properly protect players from the type of athletes that are currently playing the sport at it's highest levels.