I think it's an exaggeration of the "city effect": the denser an environment is, the more likely it is that people who see you out to talk to you are going to have a negative agenda, because everyone else is trying to keep their head down.

If you meet a stranger at the North Pole, where you're the only two humans around, you're going to talk to them. If you meet a stranger in a remote village, you're probably going to talk to them. If you meet a stranger on the street in New York, you're probably going to put your hand over your wallet. Adverse selection wins.

It sometimes feels like social media has gone from a place to make friends to a place to make enemies - or at least to bond with a group through the medium of hate. Bonding through hate of the outsider is hardly new, but it's especially negative on the Internet where it can be amplified over and over.