Data Protection Commissioner Billy Hawkes revealed his office opened 783 formal complaints during 2010, with more than 400 cases related to data security breaches.
In his annual report, Mr Hawkes also criticised the use of CCTV in schools, workplaces and some village centres.
A secondary school in Clane, Co Kildare, was ordered to remove cameras it had installed in the student toilets after the students walked out in protest.
And a primary school in Co Mayo had to take down cameras it had installed inside and outside the building.
Mr Hawkes said: "Complaints concerning CCTV in schools are not confined to students.
"On several occasions, school staff complained to our office about the use of CCTV to review their movements.
"We have also encountered the use of web-linked CCTV systems to allow employers, based off-site, to monitor their staff carrying out their duties."
The commissioner revealed the 350pc increase in cases of data security breaches was linked with the newly introduced code of practice.
One investigation found significant failures within the insurance sector.
Insurance Link, a shared claims database, contains information on almost 2.5 million people for companies to share and cross-reference insurance claims.
The commissioner found too many staff members in insurance companies had access to the database with little or no oversight of that access.
Some serious incidents of inappropriate access were identified, with one employee in Zurich Insurance searching a noted celebrity who had not registered a claim.
A number of employees at Aviva and FBD also searched for a person the same day who was involved in a prominent court case.
And in several cases staff searched for family members and friends, while some used Insurance Link to check the claims history of a vehicle or property before purchase.
Other serious data security breaches investigated included the compromise of a GAA database and a hacking incident impacting on the website of SelfCatering.ie. There is also an ongoing probe into unlawful access to Department of Social Protection records.
Mr Hawkes said his report emphasised the need for accountability on the part of public and private sector organisations for the personal data entrusted to them.