Exactly. Even now that they offer official paid servers hosted by Mojang, you're still paying for your own server, and you control who's invited to it.
Parent can rest easy knowing that all the penises on their server were definitely created by their own kid and his friends.
Put in a more general way: decentralised systems sometimes avoid hidden costs that more centralised systems can suffer from. Minecraft is decentralised and Lego Universe is not.
This point in the article is really strange though. Isn't Roblox, for example, operating massive building online universe for kids and somehow solves this problem without godzillion of moderators?
If Lego can't do it themselves - just, you know, acquire Roblox.
Exclusively player-operated servers. This let Minecraft's online scene take off while saving Mojang from most of the overhead.