TVii was a good idea, just badly executed. Before the Wii U launched, I had noticed my friends were using something called GetGlue to report on what they were watching, but you weren't allowed to find out what GetGlue was about until you committed to registering up for the service. Since the name "GetGlue" brought up mental images of The Simpson's Ralph, it didn't seem like such an appealing thing(it actually referred to the glue on the backs of "stickers" which you'd earn with them by achieving certain... well, "achievements". Achievements in watching TV, /smh
Apparently, NintendoTVii was a collaboration with the team behind GetGlue, which allowed you to use your social networks to "Watch TV together" and comment on stuff as it happened. It was fun, but it was also free, and without special advertising or other monetization (ie: perhaps getting a cut from cable companies), so Nintendo wasn't making any money off of the service, so if it didn't get popular on its own merits, it would have to be axed.
Thus, it was axed.