Nintendo have announced that they have temporarily removed Pokémon Bank from the Nintendo 3DS eShop. This is following the massive influx of users on both Nintendo 3DS and Wii U coming on Christmas, plus the addition of Pokémon Bank causing the Nintendo Network to drive to a halt. This means users cannot download it anymore and currently cannot access the features of the game.. It is currently unclear when Pokémon Bank and Poké Transporter will return, or if the western release is delayed. They have made it clear that the 30 day trial for previously registered users will restart when it returns.
Edit @ 13:14: Pokémon Bank is now listed with a release of TBD (To Be Decided) on the North American and European eShops. We'll bring details on this as soon as we can