Console and DVD users are very familiar with the region-lock concept: companies divide the world into sub-regions, and make sure that content bought in one region only works there. There are many reasons, but it mainly has to do with price control. This allows the company to sale games for a higher price in countries where the market can afford it, and lower the price in places where the market can’t bear higher prices. But for this to work, one needs to avoid imports from lower-priced regions, hence the lock.
The Nintendo 3DS has been confirmed to be locked. Those who have tried buying games from another region have found that 3DS games don’t work (DS games do). It’s usually not a big deal for most users, but it could be an annoyance for the enthusiast who can’t wait to get a console, or a new game which came out abroad.