Mojang has recently released their "Minecraft Realms" service in North America (it is already available in most of Europe). Minecraft Realms is a subscription service that allows players to have their own small, private server to which they can invite their friends and play together online without the hassle of setting up their own persistent world.
This is a really neat addition to the game, and it has been wanted for a long time. However, Mojang's implementation of it has exposed my children and any children that play (or have ever played) on any multiplayer servers to potential very easy targeting by child predators.
The problem is the way in which players can invite their friends to their Realms servers. All that is needed is a username, and the invited player will receive a notification that they have "been invited to so-and-so's Realms server".
This becomes a problem when a child predator joins "family-friendly" or "kid-friendly" servers, and can get a list of dozens to hundreds of usernames that are primarily young children. Normally, these servers are moderated and all communications and connections are logged, so that if anything were to happen as a result of communications on them there is a record of those conversation and IP addresses that can be turned over to authorities. However, a child predator could send Realms invitations to these kids, with no record or knowledge by the server staff. In fact, on many servers, the predator would not even have to connect to it, since lists of players can often be found on websites or online world maps.
Less internet-savvy kids would gleefully accept any "invitation" thinking they were the recipient of something special. Once on there, all bets are off as far as their safety and security.
At the very least, you should make your kids aware of this and instruct them not to accept these invitations, unless they know the person in real life.
I have opened a suggestion on Reddit in the /r/Minecraft and the /r/MinecraftSuggestions subreddits (the "official" suggestion inbox), to attempt to get some attention to this glaring safety issue. Myself and some other parents are asking for Mojang to add a "Parental Controls" menu to the game, which will allow parents to restrict what multiplayer servers and Realms servers that their kids can connect to. We would like this to work similarly to the v-chip in your television: parents could restrict their kids from receiving Realms invitations, and also from joining multiplayer servers unless a parent approves it. Unfortunately, the demographic of those subreddits is a bunch of 13-16 year old kids, and they aren't too keen of the idea of giving their parents control over what they do on the internet.
I would like to ask that if your kids play Minecraft, and you would appreciate having some parental controls over what servers and private Realms servers you kids have access to, that you would let Mojang know and help us get this done. You can show your support by tweeting the developers (@jeb_, @Dinnerbone) and Mojang support (@MojangSupport), by posting on their Facebook page, or by voting on and expressing your concern in the comments of the Reddit posts that have already been made. You can find them by searching for 'cheracc' (my username) on Reddit.