As said earlier, Nintendo is serious about making Miiverse into an elegant online service for a more civilized age. They want to keep it safe, too, and make sure some adult in the house is aware of what the kids are doing on it.
The best way to accomplish that seems to be requiring a nominal fee, payable by credit card, to register a minor on Nintendo Network. The price is $0.50.
We put this to the test at Kotaku and while there is a means of lying about your age to get a Nintendo Network ID, Nintendo has at least tried to weave things to catch junior in a lie.
This is what happens:
When creating a Nintendo Network ID, the first thing the system does is spit out a warning that says if you are under 18 years old, you have to get your parent or legal guardian to approve your use of the service. OK. Sounds good. You button 'yes,' whether Mom or Dad really have said 'yes.' Either way, you're then taken to a profile screen asking for your birthday.
Answering that honestly then triggers the console's parental controls, if they aren't already active. This can be fine if a kid is creating an underage profile with his parents' consent. For those who aren't, they now have to either defeat the parental control or, if that hasn't been set yet, create the PIN and security question answer that establishes them.
Let's say junior then decides to set up the parental controls (which could, down the line, result in a parent asking why parental controls had been set on the machine already.) He'll still have to follow that up with the 50 cent credit card payment to create his profile on Nintendo Network, on the assumption most minors don't have a credit card.
Ah, you say. What if I'm 14 years old and just lie all the way through, and put in my birthday as 18 years old? You can do that. And you've created a profile that says you're 18.
It's not a perfect system, and can be defeated early on by a child determined to lie. But as I learned when I was a kid (well, I wouldn't say I learned as I persisted with the behavior) a second lie doesn't eliminate the chance to be caught, it multiplies it. And Nintendo's still performed its due diligence.
And, yes, you still need a credit card to buy something from the eShop.