So... many... penises....
Approaching it with all the trepidation of a toddler entering a dark basement (of dick jokes), Nintendo feared that open communication with internet users would immediately expose its players - in this case, children - to objectionable material.
It turns out that Nintendo's fears weren't entirely without merit, as a recent spate of complaints caused it to shut down the SpotPass Feature on the 3DS' Swapnote app.
Worse - and more interestingly - it did this move almost overnight, with no warning given or action required from users.
For those unfamiliar with Swapnote/Letter box (or the 3DS in general), it's a native app on the handheld that allows users to share notes, drawings, and - recently - pictures with people over the internet. The catch is that you can only share notes with friends that you register to your 3DS, a process that requires you to enter a 12-digit code generated from the friend's 3DS.
Until recently, the exchange of friend codes was something you did with - well - friends.
Most gamers would know, at best, a handful of fellow 3DS owners and so the Swapnote feature was a great (if rarely used) way to exchange friendly notes, silly jokes, or crude drawings with far-flung friends. Unfortunately, two things happened recently to open up the floodgates of friend code exchanges: Animal Crossing: New Leaf and Pokemon X/Y.
Both games provided users with excellent incentives to add a raft of friends, and so players - young and old - turned trustingly to internet forum boards in hopes of blithely finding like-minded gamers to swap friend codes with.
These players found what they wanted for the most part, but some bad apples snuck in with the majority of players because, well, internet. Nintendo acknowledged the forum board code swap problem in a news post on the official Swapnote page:
"Nintendo has learned that some consumers, including minors, have been exchanging their friend codes on Internet bulletin boards and then using Swapnote (known as Nintendo Letter Box in other regions) to exchange offensive material.
Nintendo has been investigating ways of preventing this and determined it is best to stop the SpotPass feature of Swapnote because it allows direct exchange of photos and was actively misused."
It's not really known how many complaints Nintendo received or how many penis pictures were sent across the service, but I'm guessing the answer is somewhere between "more than one" and "lots".
Also not known is whether Nintendo ever plans to flip the switch back on for SwapNote's SpotPass feature, but at current it looks like 3DS owners just lost a great little toy because of the darker and more juvenile side of the internet.