Here's a few brief articles and links about the disinhibition effect...i don't believe a large quantity of people create a completely false identity, more of an embellishment of true characteristics...this also leads to "over-sharing" or intentionally withholding information

our very own DocJohn wrote a brief article about this effect:
Online Disinhibition Effect | Encyclopedia of Psychology


The online disinhibition effect. [Cyberpsychol Behav. 2004] - PubMed - NCBI

The Online Disinhibition Effect ? PsyBlog

so, now that I have thrown your thread way off track...

ultimately, the world is shifting more and more towards virtual relationships...and to get back to your original point...if you are interested in a girl you meet through social media...my best advice would be to start as friends and go from there...just like in real life...coming on too strong can cause her to retreat...