You guys do realize that a shodan is more or less equivalent to a high school diploma, right? And all a high school diploma means is that you can (hopefully) read, write, and do some simple sums. You aren't an expert in anything. In essence, all you know is technique. And most of the people getting high school diplomas are 18 or younger...maybe we should raise the graduation age while we're at it. Do 18 year-olds really have the maturity to get jobs, sign legal contracts, vote, enlist, or go to college?
Thing is, maturity isn't something that comes with birthdays. It comes with experience. There's all kinds of things that can kick a teen-ager into adulthood before they hit some magic number of years.
I realize that the analogy for shodans works best with the American education system. I understand that in Europe you can get out of high school with some real qualifications. Unfortunately, the American system is the only system I'm really familiar with.
I suppose if you're going to set an age limit, 16 makes as much sense as anything. If you can drive when you're 16 you might as well be able to get a shodan as well.
And, for what it's worth, I find working with beginners rather challenging. They do the oddest things, both to their partners and themselves...