I noticed that there are normally age limits to donating blood, 17 being the most common. Why must there be an age limit? Isn't a 16-year-old's blood just as good as a 17-year-old's? I can't imagine it would be that bad for a person's own health to donate blood. Is it because of responsibility? Like a kid might try and uh, donate more blood than he should? Seems like people normally care about themselves and don't donate when almost anybody could.