Data privacy is a major concern for the majority of web users, according to new research.

A survey of over 4,000 adults who regularly go online revealed that 80 per cent were worried about their privacy and that the concern increased with the age of the respondent.

The survey, conducted by advertising firm Burst Media in December 2008, is released at a time when an increasing number of social networking sites are forming advertising deals that enable businesses to target users based on their profile data.

For example, Facebook recently launched a Polling Ad that allows marketers to poll a selection of users based on their age, sex, or likes and dislikes, while professional networking site LinkedIn sells advertising space at a cost that is based on the professional position of the user a business wants to target.

A new targeted marketing service has also been launched for micro-blogging site Twitter that allows advertisers to monitor Twitter posts for keywords and then send users pre-determined advertisements.

The Burst Media survey found that three out of five web users are aware their behaviour is being tracked online but that nearly 80 per cent disliked giving up their personal privacy for more relevant advertising.

"Advertisers must take concrete actions to mitigate consumers' privacy concerns and at the same time continue to deliver the message as effectively as possible," advised Chuck Moran, Burst Media marketing vice president.

Moran also said publishers need to be completely transparent about their privacy policies following the Facebook terms and conditions controversy.

Earlier this month, Facebook changed a clause in its terms of service without users' consent that technically allowed the company to keep ex-member data forever and use it for commercial purposes. In response to thousands of protests from social networkers, Facebook has since reverted back to its old contract terms.

A report by Burst Media following the survey advised web publishers to be " fully transparent" when it comes to collecting web site visitors' information.

"Have an easy-to-find, clear, and concise privacy policy that unambiguously states what visitor information you collect and how you use it," the report said.