Update:
Nintendo has posted a brief message further explaining how the eShop process will work:
The Nintendo eShop will be offline at different times around the world to manage traffic volume until full operation is restored.
— Nintendo of America (@NintendoAmerica) December 27, 2013
Original:
Nintendo 3DS or Wii U owners attempting to access the eShop will likely be greeted with an error code as Nintendo has temporarily disabled the service in an "effort to manage the high volume of traffic and ultimately improve your experience."
Nintendo announced this morning that the eShop would be temporarily taken down and it appears the time has come. According to today's statement, the eShop will remain offline between the hours of 4:00pm ET and 4:00am ET. In the statement, Nintendo apologized for the recent issues plaguing the Wii U and 3DS online services since Christmas, including the inability to create Nintendo Network IDs or access the eShop.
Prior to taking the eShop offline, Nintendo of America tweeted, "We are determined to make sure everyone can enjoy all that Wii U and 3DS have to offer. We will keep you updated."
Wii U and 3DS owners can keep track of Nintendo's online service status here, but we'll be sure to let you know if anything new should arise. Right now, it's status quo as all Nintendo platforms are experiencing the vague "technical difficulties."