Register it now to Club Nintendo
I downloaded Tank! Tank! Tank! yesterday for free on the Wii U eShop, and I have to say, despite the fact that it may not be worth a full retail asking price, it's a great time-wasting free download. But it seems as if that's not the only thing it's good for, as an astute reader pointed out this morning that the game also counts towards your Club Nintendo membership.
If you simply connect your Club Nintendo account to your Wii U (a one-time requirement) and download Tank! Tank! Tank! from the eShop, you'll score 60 coins right off the bat, and 10 coins for a post-game survey. Whether this is a mistake on Nintendo's end or intended (the listing does note "download version" after all), one thing's for sure -- go download the game now even if you have no intention of playing it!