Users are self censoring their day-to-day activities to avoid disapproval from online friends and family.
Now scientists warn that the fear of constant surveillance has led to a blurring of our online and offline lives and reduced our freedom.
The study of more than a hundred 19 to 22 year olds revealed they would hide cigarettes if pictures were being taken at parties for fear of being frowned upon for smoking.
It included in-depth interviews with 28 of the participants and experiments involving a further 80.
Others admitted avoiding standing next to certain individuals for fear of a picture being taken that would damage their relationship with a partner.
The phenomenon has been dubbed the 'extended chilling effect' and been likened to Big Brother in George Orwell's frightening 1984.
Participants also said they avoided taking pictures altogether in certain circumstances, such as sunbathing on a beach, for fear the images would attract unwanted attention online.
One student 'Emma', 20, whose name has been changed to protect her identity, said:
"At parties every time a picture was taken I put the spliff behind my back so people on Facebook don't think I'm a constant druggie.
"If the photo was not going to end up on Facebook I wouldn't care as much, because not everyone would see it because it's a lot more public, you know, with Facebook."
Another 'Shelly', 21, added: " I remember during freshers' week I had a boyfriend, and he was really jealous and he saw some pictures of like me on someone's shoulders or something with a different boy and just like went mental at me, so I had to, like, consciously think every time there was a camera out like 'oh, am I standing too close to this boy?'"
Dr Ben Marder, lecturer in marketing at Edinburgh University, warned there was a blurring of our online and offline lives as mobile cameras made people possible subjects of surveillance at all times.
He explained: "At a time when any our offline lives can be instantly captured on a smart phone and posted online, people are becoming less free to act as they would like, as their boss, partners and families could always be watching.
"What started as a tool to bring warmth to our relationships, has started to have a chilling effect on our behaviour. Big Brother might not be watching, but our Facebook friends are. And it is reducing our freedom."
Dr David Houghton, of the University of Birmingham, said: "The increased accessibility of our personal persona to different types of people online make our offline lives a trickier juggling act than ever before.
"A once seemingly innocuous photograph or video clip can now be the subject of more persevering anxiety, and our research shows this extends to bridge the gap between our online and offline lives."
Previous research has established the 'chilling effect' where people constrain the self they present online due to peer-to-peer surveillance on social network sites (SNS).
But this is the first time the possibility the threat of being watched on these might change behaviour in the real world, known as 'the extended chilling effect.'
The researchers said: "The purpose of this study is to examine the existence of this 'extended chilling effect'.
"Drawing on theories of self-awareness and self-presentation, the impact of surveillance in SNS is theorised to lead to an awareness of online audiences in offline domains, stimulating a self comparison process that results in impression management."
They said the results provide support for changes in everyday behaviour in order to "avoid an undesired image being projected to online audiences."
Added the researchers: "The novel finding the chilling effect has extended highlights the potential dangers of online peer-to-peer surveillance for autonomy and freedom of expression in our offline lives."