2014 — Adobe: Sep 17th 2013, 152.0M records
Technical writeup
Sep 17th 2013. Hackers obtained access to a large swathe of Adobe customer IDs and encrypted passwords & removed sensitive information (i.e. names, encrypted credit or debit card numbers, expiration dates, etc.). Approximately 38 million Adobe customers. Updated: Now 152m (May 2014)
Root cause
Hacked