There does not appear to be any malevolence at play in this incident. According to CNET, one of the largest banks in Japan has lost hundreds of thousands of customer records as a result of combining different IT systems. I call it an "incident" because the code of fair information practices requires a custodian to protect information against loss.
Lost: Data from 270,000 bank accounts | CNET News.com:
"Japanese bank Mizuho said it has lost the confidential data of 270,000 account holders. Mizuho Financial Group, which owns the retail bank, said it had lost customer account numbers and names at 167 branches over several years, according to a Financial Times report on Wednesday. The bank is said to have suffered problems integrating systems and managing data since it was formed three years ago...."