Nintendo has learned that their Swapnote service was being misused to exchange offensive materials over Spotpass and decided to just stop the service for now.
The inappropriate was allegedly happening over Internet bulletin boards where some consumers including minors are involved. They exchange friend codes, and exchange offensive materials which could include photos.
Here's the official statement from Nintendo taken from their website.
"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.
Nintendo always wants to provide a positive experience for all consumers and limit the risk of any inappropriate activity or misuse of a service. We feel it is important on this occasion to take this action.
We are very sorry for any inconvenience to the many consumers who have been using this service responsibly; however this decision was made considering the point that many minors also use this feature of Swapnote. Thank you for your understanding.
Nintendo will continue to work to ensure more consumers are aware of our Parental Control features, which allow parents to manage their children’s experience on our systems."It might be useful to re-iterate that this only affects the Spotpass feature of Swapnote, special services and affects all regions.