https://en.wikipedia.org/wiki/Betfair#Data_theft
In September 2011, Betfair admitted that it had concealed the theft of confidential customer data from the company's 2010 share prospectus. The theft included the payment card details of most of its customers, "3.15m account usernames with encrypted security questions", "2.9m usernames with one or more addresses" and "89,744 account usernames with bank account details". The company further stated that it had informed the Serious Organised Crime Agency of the incident which happened on March 14, 2010 but was not discovered by Betfair data security until May 20 of that year.