And it's Cubic Ninja.

Apparently the cart can be used to play homebrew (tisk tisk) on the 3DS, and is now being recalled.

Grab a copy if you still can.

So that's why this surged on amazon!

$61 from amazon.ca or $50 for amazon.com... Yea I will wait... Not like I can do anything till the n3ds as well as the backup launcher comes along anyway since I don't want to get banned from Nintendo's online

It might rise in price if the units are being recalled though.

Yea but there will always be other ways to hack it. Ironically, this is by ubisoft lawl (cause of how anal they have been against piracy). Thanks Ubisoft

Won't Nintendo just update the system again? Or would that not solve the problem for some reason?

It should but I doubt Nintendo knows what the vulnerability is at this point or else they would have already sent a patch for it! But of course, the key is for hackers is that by this point, those that want to hack will not update their 3ds anymore until a "spoof" comes out

It didn't sell many copies, so it should become a true "rare" game (as in low quantity/hard to find).

Whether or not it remains valuable (what many seem to confuse with rarity) depends on demand.

this was like 3 pounds in shops a few years ago! how did it get so rare and.... how can this be used to play homebrew games?

From what I gather it has to do with the level editor in the game. Dodgy save files can be loaded through the editor to allow homebrew.