Club Nintendo of Japan has been hacked, and apparently full names, addresses and phone numbers were a part of the leak. Nintendo informed them that the breach "only affects Japanese members," so if you're part of that program, definitely log in and change your password now.
The hack allegedly began on June 9th, and took a month to detect, after 23,000 unauthorized logins. Wow! Nintendo is responding to the hack with new preventative security measures, so hopefully it won't turn out that the intruders were able to access any other data.