Some have indicated that narcissism is influenced by parental behavior in this way that @-Asdfgh- has mentioned. Narcissists often have parents who simultaneously belittle them and praise them. Often the praise is unjustified or for trivial achievements. The narcissists deal with the belittling by telling them everyone around them is a jerk, by aggrandizing their achievements and seeking negative supply. Negative supply (pleasure from hurting others) is a lot easier to get than the healthy forms of supply (true admiration for valid talents, true love, self-respect from exercising discipline, showing kindness in the face of bad treatment from others -- all the things empaths show). Think about it. If I want negative supply, all I have to do is walk up to any random person and insult them. I can hop on Facebook and make an inflammatory comment to someone I don't know. Often the effect is immediate. The other positive sources of supply take a significant amount of effort and often, the fulfilling effects aren't visible until a significant amount of time has passed, if ever. For the empath, often, virtue is its own reward with no external effects whatsoever.
Much of this is true, although my point was originally more that those with low self-esteem (e.g. those who are depressed) may seek out ways to defeat themselves such that the world matches their low self-esteem, or at least part of it. People are not simple in the sense that low self-esteem and belief in having worth may exist simultaneously. I can see why, in the past, people ascribed names such as ego and id to these various contradictory elements.
In terms of social media I can see how it could be a way to create a sort of superficial positive supply. That might be good, if an adjunct to positive supply in depth, e.g. get someone over a low point, but not as a substitute.