Expedia’s Trip Advisor, email marketing provider Epsilon, Sony’s online entertainment services, professional engineering society Institute of Electrical and Electronics Engineers. They all suffered some kind of a data breach in the first four months of 2011. At one point, it seemed like there was at least one new security breach being reported every week. Here are eWeek's 10 biggest data breaches of 2011 to date.

1. Sony’s PlayStation Network, Qriocity, Sony Online Entertainment

Date Reported: April 26
Size: 101 million user accounts
Type of Data: name, home and e-mail addresses, login credentials, some credit card information

2. Epsilon, Alliance Data Systems

Date Reported: April 1
Size: Unknown; 60 million estimated e-mail addresses
Type of Data: e-mail addresses, some names

3. HBGary Federal

Date Reported: Feb. 7
Size: 60,000 records
Type of Data: corporate emails, presentations, client reports

4. WordPress

Date Reported: April 14
Size: Unknown, 18 million records estimated
Type of Data: source code, API keys, passwords

5. University of Southern California

Date Reported: March 4
Size: 31,000
Type of Data: names, addresses, health records, financial data, Social Security numbers

6. TripAdvisor, Expedia

Date Reported: March 24
Size: unknown
Type of Data: user e-mails

7. RSA Security

Date Reported: March 18
Size: Unknown
Type of Data: "information related to SecurID technology"

8. HuskyDirect.com, University of Connecticut

Date Reported: Jan. 11
Size: 18,059 records
Type of Data: names, addresses, credit card numbers, e-mail addresses, phone numbers

9. Seacoast Radiology

Date Reported: Jan. 12
Size: 231,400 records
Type of Data: patient names, social security numbers, addresses, phone numbers

10. Ankle and Foot Center of Tampa Bay

Date Reported: Jan. 29
Size: 156,000
Type of Data: names, dates of birth, addresses, social security numbers, health care services received

Read the full report here: http://www.eweek.com/c/a/Security/10-Biggest-Data-Breaches-of-2011-So-Far-175567/