I wouldn't think it's a mistake. Supposedly they were having trouble getting their shipment of the systems, but now they have them coming in, so a delay makes sense. In reality, I think that after their issues selling off their stock of the original 3DS last year, they were waiting to see how popular the new model was by watching third party sales and those through other retailers. Since the reviews are high and they seem to be selling strong, maybe Amazon decided over the last few days to give it another shot and sell the system. That's just a theory, but I find it hard to believe that Amazon, of all retailers, would have difficulty getting their stock by the launch date.
What I don't understand is why Amazon hasn't carried not only the 3DS but the DS line of handhelds as well as the Wii console for the last 1 to 1 1/2 years. I've heard the whole shipping issue reason with the 3DS but that doesn't explain why they're not selling the Wii. I personally think the whole shipping problem excuse is bull b/c all of the international Amazon sites have been continuously selling the Nintendo handhelds and console.
I've been wondering if Nintendo of America has been the problem. The last couple of years NOA has been acting stupid with not bringing games like Xenoblade Chronicles and The Last Story here until the fans begged and pleaded with them to. Then when they finally brought Xenoblade here they made it where you could only get the game through their site or through Gamestop. I really hope Amazon doesn't have this problem with the Wii U when it comes out in a couple months.
Until Amazon or Nintendo make an official statement, we'll be in the dark and frustrated. We can speculate endlessly, but only Amazon and Nintendo know the real reason, neither seem to care about what the public thinks of them over the dispute.
strange they still don't sell it, and now they won't be stocking Wii U either. Clearly something happened between the two and they don't wish to resolve it. Its more Nintendo's loss really, not being on Amazon is a pretty large gap in online sales.