The point of a girl "rejecting losers" on a dating site has nothing to do with the losers and everything to do with reinforcing her self-image of "the kind of girl who turns down 10 guys a day". Same with the people who write long e-mails saying "you suck": if someone is looking for it, they can find a lot of evidence people around them suck. The point of writing e-mails about it is to build up one's own confidence, heal some hurt, or vent some frustration about some issue completely unrelated.
The stories are really about people creating a self-image and protecting an identity (call it "reflexive brand management", if you will). While I'll concede that they're narcissistic in their disregard for how their actions affect other people, I think both are natural and healthy in terms of their own psyche.