If you want to buy a video game for a Nintendo platform as a digital release, then you're basically limited to Virtual Console titles, fun little quirky titles such as Pushmo, or bizarre shovelware titles that nobody should want.  While Sony and Microsoft have rushed onward to offer first and third-party releases via PlayStation Network and Xbox Live, Nintendo has been hesitant to put its gold in a digital pot at the end of an online rainbow*.  Starting in August, however, you'll be able to buy full retail titles such as New Super Mario Bros. 2 via the Nintendo eShop and save them to your favorite SD card.  Game Informer explains:

[Satoru] Iwata says that customers will have a choice in how they purchase future first-party Nintendo releases on both the Wii U and 3DS. Players who opt for the digital route can download games directly onto their system's SD memory card through either the Nintendo online shop or by inputting a 16-digit code that can be purchased at retail. Iwata says that physically and digitally distributed formats have their own advantages, and that Nintendo wants to give players a choice. It may be more convenient for players to acquire the digital versions of games, but they're locked to the system that they're downloaded onto. Players who do a lot of game swapping with friends will have to stick with physical copies of their games.

While I have gone for downloadable purchases in the past, I always prefer physical media when it's available.  I'm a collector.  I keep all of my games along with their original packaging, manuals, and other materials.  I like having a shelf packed with memories in the form of small plastic objects.  While downloading Mario's next adventure may be more convenient, I'd miss out on looking at the box art, tearing open the plastic wrap, and the enjoyment of inserting the game card into my 3DS.  You get back to me when the Internet can provide that.  Still, I know there are many people out there who want to get out of the habit of collecting cartridges and discs, so I'm glad that Nintendo is providing a digital option.  However, I intend to avoid it as much as possible.

* You like that line?  I worked hard on that one.