Social network sites are great for meeting new people and expressing who you are. You can find like-minded individuals, and in some cases can become internet best friends. The added anonymity means that those who are too shy/scared to be themselves in real life get an outlet, and a chance to really express themselves, which is especially popular on Tumblr.
Tumblr users are brilliant for capturing trends and turning them viral, but there can be a massive negative to this. Over the past year or so, the chosen “trend” has been focused on mental disorders. There have been many petitions to raise the awareness of mental and social disorders so help can be more easily given. There has also been a massive rise in people identifying as “socially awkward” because they think it’s a quirky trait to have, and reblogging images of melancholy quotes that they can sometimes relate to.