For one of my research projects I looked at how social media affects self-esteem. The result found that those who were heavily engaged in many platforms of social media (Facebook being the main one) had lower self-esteem than those who used other websites and had limited use and access to social media.
IMO, it could be. I mean, look at the university section. Many people post about their offers - not with the intention of bragging, just to say how their interview went and the results from this. I don't know about anyone else, but for me I'd feel pretty hurt and discouraged to see someone post about getting an offer from my top university choice for the same course, whilst I was rejected. In actual fact, reading peoples GCSE grades has made me feel crap before on this site, and I sat my GCSE's 4 years ago, but it still hurts comparing grades to my own, especially of those who ate applying for my uni choices. Always makes me question myself and ask "what's the point of applying if these people with better grades are, too?"