http://club2.nintendo.com/30/
Probably as a promotion to the upcoming crossover game. If you register Fire Emblem: Awakening and Shin Megami Tensei IV on the US Club Nintendo by August 31, you'll get $30 eShop credit (which is redeemable on either the 3DS or Wii U).
Feel free to move this thread to the more apt board, or lock if repeated (I didn't find anything).