So, the 3DS went on sale in Japan YESTERDAY and it appears that thieves and hooligans are already able to have their way with it. Despite being built to tackle piracy, Nintendo's latest handheld has been "hacked" for use with R4 cards, at least according to Japanese gamers who posted their antics on Youtube.
Bear in mind that, since this uses an R4, only the DS side of things have been infiltrated. You won't be able to steal -- sorry, "back up" -- your 3DS games just yet, but it seems you'll be able to do it with your old DS library.
Although most are calling this a hack, some argue that the use of an R4 Card isn't "hacking" per se. Whatever you want to call it, the 3DS' software has been bypassed in order to get the cards running, so it's dodgy no matter what label you want to slap on it.
As far as the dedicated 3DS software goes, only time will tell if that's an uncrackable nut. Probably not.