It seems pretty impractical though. I heard it's just a cart emulator, doesn't have an OS yet (it's still in the works apparently), so you can't load multiple roms into it. Also, doesn't seem they have made an emulator for it. Nonetheless, once the Miiverse firmware update comes out, I'm sure it'll block the flash cart, and will be a good incentive for everyone to update to.
They say that they're working on a custom OS - which implies that they are able to execute arbitrary code. Which I can't really believe, and even if they can it will get patched by Nintendo for sure.
I'd love to get some code running on the 3DS, but I don't think that this device will allow me to do that.
This news is rather old, there were 2 other Cards doing the same thing, like 2 months ago.
But honestly, I don't think it'll be a success, Pirates don't really like buying multiple Micro-SD Cards per ROM, and it's probably Region Locked too.
I'm just waiting for Nintendo to crack down on it. It'd be one thing if they showed it running homebrew and said they're not developing it for piracy, but they explicitly showed it playing pirated 3DS games, it's only a matter of time till Nintendo issues that cease and desist