People, including NeoGAF, are missing the vital point why Nintendo is doing this. It's not to sabotage for people who wants to import games.
Recently, Nintendo has been in legal battles with manufacturers of devices such as the R4 chip. These devices not only allows people to do homebrewing and play imported software (which very harmless) but the ALSO allow people to play copied games on their DS. Recently in the UK, Nintendo won such a battle and while new manufacturers undoubtely will plop up, a big step has been taken as far as legal concerns. Remember, not long ago R4 wasn't even illegal in the UK. With a thing like this decided in court, it'll be much easier for Nintendo to track down these companies and kill them.
So what has this to do with things? Well, the reason the judge went Nintendo's way was because the R4 chip bypassed a security lock of the system. The R4 manufacturer said that it's simply a software program, similar found on regular PCs. But in contrast to a regular software program, R4 bypassed the console's natural security.
By putting in region locking in the 3DS, these manufacturers will have to bypass that too, making an illegal act which Nintendo easy can track down now that it's actually illegal (in the UK at least). Of course someone in Hongkong will hack the 3DS in a week after it's been released, but everyone already know that, including Nintendo. The best thing they can do to stop piracy and copied softare is to play by the rules, and that's exactly what they're doing with the region lock on the 3DS.