Apple has offered some clarification on the situation regarding the SIM lock on iPad with Wi-Fi + 3G units sold in Japan. It was originally reported that all iPad with Wi-Fi + 3G models sold in Japan would be SIM-locked to SoftBank. Only a few days later, according to a Mobile in Japan article, Apple CEO Steve Jobs responded to a customer email by saying that “[a]ctually, the version of iPad sold in Japan does accept international SIMs.” This was contradicted by information on Apple’s own website, which stated that users could not use a micro SIM from another country in iPad with Wi-Fi + 3G units purchased in Japan. Apple has since told the Wall Street Journal that Japanese iPad with Wi-Fi + 3G models will only work with SoftBank in Japan but are unlocked for use with other carriers abroad; whether or not iPad with Wi-Fi + 3G units purchased outside of Japan will work in Japan will depend on the roaming agreement of the user’s carrier.
Japanese iPad with Wi-Fi + 3G SIM lock explained

Charles Starrett
Charles Starrett was a senior editor at iLounge. He's been covering the iPod, iPhone, and iPad since their inception. He has written numerous articles and reviews, and his work has been featured in multiple publications.