Rumors about Nintendo Network have been at least partially confirmed. Nintendo president Satoru Iwata announced at an investor’s program that the service will not be a re-brand of the Nintendo Wi-fi Connection, and that it will be supported by both 3DS and Wii U.
"Unlike Nintendo Wi-Fi Connection, which has been focused upon specific functionalities and concepts, we are aiming to establish a platform where various services available through the network for our consumers shall be connected via Nintendo Network service so that the company can make comprehensive proposals to consumers,” Iwata said.

Yep, it's for real.
Nintendo outlined three key features.
First, it will support personal user accounts. Online profiles are no longer tied to each system, meaning gamers will be able to log into their accounts on friends’ consoles. Iwata said this will offer “a variety of different services and content.”
Second, Nintendo Network will offer digital distribution of packaged software. Nintendo is exploring the possibility of making full retail software available through Nintendo Network, but there’s been no word on when it’ll happen.

The new Fire Emblem will be Nintendo's first effort at DLC.
Finally, paid downloadable content will be available for Wii U and 3DS. Games like Fire Emblem: Kakusei and Square Enix’s Theatrhythm: Final Fantasy have been confirmed as DLC-supporting titles. Iwata confirmed that Nintendo will not require players to buy downloadable content to get the full experience from its software.
"As a software maker, Nintendo believes that its packaged software should be sold to our consumers in a form so that the consumers will know in advance that they can enjoy playing the software they purchased just as it is," Iwata said. "We believe that our consumers will be able to feel more secure if we offer our add-on content as an additional structure in which those who love the game will be able to enjoy it in a deeper way for a prolonged play time."
Iwata ended the presentation by saying that Nintendo will strive to achieve both first- and third-party compatibility to ensure customers’ satisfaction with Nintendo Network.
Aaron Kinney, NoobFeed