The poll suggests 51% of internet users belong to social networking sites
Almost 80% of social networking site users would be more careful about the details they put online if they knew the media might use them, a poll says.
The Press Complaints Commission said 89% of the 1,000 people polled wanted guidelines on what the media could use.
And 42% of 16 to 24-year-old who used such websites said they knew someone who had been embarrassed by material which was posted without consent.
The PCC is opening talks on how it should respond to the issue.
The chairman of the PCC, the publishing industry's self-regulating watchdog, Sir Christopher Meyer, said personal information was being put into the public domain on an unprecedented scale and that this had serious ramifications for the regulation of media outlets.
"This clearly has implications for the PCC, which has always had the task of deciding where to draw the boundaries between what newspapers and magazines may legitimately publish and what can rightly be considered private," he said.
"The challenge remains the same for online editorial content, including material taken from social networking sites.
"In the digital age, self-regulation, with its sound principles and speed of operation, has never been more relevant."
The poll, which was conducted for the PCC by Ipsos-Mori, also found that 89% of internet users polled said there should be clear guidelines about what types of information could be used by the media.
They said that this would allow people to complain if the information published about them was wrong or intrusive.
The poll also found 49% of respondents said it was wrong for the media to use information they had posted on line without asking the consent of the person concerned.
And 58% were fairly or very concerned about the lack of control about how they were depicted on websites.
And of social networking site members, 55% considered whether personal details such as photos might be used by someone else without their consent, before posting them online.
Sir Christopher said the PCC's current code of practice would be able to handle complaints about media outlets using material skimmed from networking sites.
But he added: "There are wider cultural and other issues going beyond the PCC to be debated, which is why we have taken the initiative of conducting the survey."