The real question is how children are spending hundreds of dollars online without parental consent.
The contract doesn't only apply to kids, it applies to everyone. So saying this is a "poor decision" because you don't want to encourage kids to use their parents credit card... is a poor argument.
(as an aside - I know zero kids that play minecraft, but I know an awful lot of adults that do... so let's not just jump and assume it's only kids playing this game).
As a player, Minecraft is only free-to-play if you voluntarily pay a server owner. If someone doesn't like a server, log into a different one! If you want to put in dozens of hours on a world without fear of it being griefed/having the rules changed, run your own small server!
My thesis is that this is basically a non-issue. If Mojang wants people to know they're not the ones charging for server access (the parent anecdote in the article), they should have a big, permanent banner in the server browser: "If you're paying for items on a server, you're paying too much! Minecraft server access is free by default!" and so on.
Some ten year old kid wants a $300 item on a Minecraft server. The kid has been told he can't use his parent's credit card without permission, he knows he can't, but guess what: even good kids break the rules, and he knows his parents have the money. He just saw them write a $5,000 check for his private tuition! (they want to raise him right) That $5,000 check though left them with $200 in the bank for the rest of the month...
I'm not for or against server monitization, but trying to blame the parents is ridiculous. Kids are not exact molds that their parents have shaped.