Because the social network is large and includes dozens of people who already know you offline, if you lie about your age, occupation, or other such information, these people will know.
In addition, as I mentioned earlier, online communication with individuals that we know offline is marked by less lying than in-person communication, and the Facebook social network to a large extent involves presenting information to those in our social network.
Online daters realize that while, on the one hand, they want to make the best possible impression in their profile, on the other hand, if they do want to pursue an offline relationship, they can’t begin it with outright falsehoods that will quickly be revealed for what they are (Toma et al., 2008).
While the presentation of one’s personality on Facebook is likely to be relatively accurate, people do have a tendency to try to appear than they really are, by highlighting positive events and emotions over negative ones (Qiu et al., 2012).
It’s difficult to lie about factual information on Facebook, unless someone is fabricating a completely false identity with a fake profile.
One survey of over 5,000 users of online dating sites asked them to rate, on a 10-point scale, how likely they were to misrepresent themselves in areas such as appearance and job information (Hall et al., 2010).
The average rating on these items was about 2, indicating a relatively low level of deception overall. They're especially likely to be dishonest in how they describe their physical appearance.
This means that if you meet people via Facebook, you’re likely to be getting a relatively accurate impression of their overall personality. Some people are more prone to deceptive behavior online than others, such as those high in sensation-seeking, and those who show addictive behavior toward the Internet (Lu, 2008).