Under Review: 
No Review
Date Breach Made Public: 
February 2, 2013
San Francisco , CA
United States
California US
Records Breached: 

250,000 (no SSNs or financial information exposed)

Breach Total Number: 
Year of Breach: 
Type of organization: 
Type of breach: 

Online attackers were able to access the usernames, email addresses, session tokens, and encrypted passwords of 250,000 users.  Twitter notified affected users and told them to create a new password.  Anyone who used the same password and username or email combination for other sites is encouraged to change the password on other sites as well.

UPDATE (03/11/2013): Facebook, Microsoft, and Apple were all affected by a similar breach around the same time.