. . today's kids don't develop a suspicion of the word "free" until they're about 24 years old. I suspect their suspicion of other sales pitches is similarly weak until that age.

Naturally, our government is anxious to recruit the required quota of canon fodder from the 18 to 23 year olds, because beyond that it's "game over". I'm sure they'd recruit them at 12 years if they could - boy could they make hay then!