As social media makes data increasingly interconnected, preserving one's privacy while ignoring the privacy rights of others may make everybody's data more vulnerable, researchers said.
"The privacy of individual consumers does not only depend on their own decisions, but is also affected by the actions of others," said Jens Grossklags, Assistant Professor at Pennsylvania State University in US.
The researchers collected data from about 400 users of Mechanical Turk, a crowd-sourced marketplace that allows members to earn money for completing various tasks.
The participants were told they were ranking versions of an app, but were not informed about the researchers' intention to study privacy valuations.
After the task, the subjects completed a survey and received payment for their participation.
In the study, the participants valued the data in their own social media profiles at USD 2.31 and their friends' data at USD 1.56 when friends' data was irrelevant to a third party app's function.
When friends' data was necessary for app function, subjects valued their own data at USD 2.04 and their friends' data at just 98 cents.
"The developers may ask for innocuous data, such as name and birth-date, but they could also want access to very sensitive data, as well as your friends' sensitive data," said Yu Pu, a doctoral candidate at Penn State.
The more sensitive data - for instance, photo files and videos - could hurt friends in a range of ways, researchers said.
Often, apps need certain types of data to function properly, but at other times, the apps do not need the information to perform effectively, although the developers still request that extra information, they said.
The researchers estimated that the average Facebook user, for example, with an average of more than 300 friends, would value the bundle of friends' data at less than a cent per friend when data collection is necessary.
When data collection is unnecessary, people value the information for a single friend at less than three cents.