Ask any serious WoW player how the game has impacted their life. From what people have told me, the social relations in-game are such that one becomes reliant on a group and vice-versa to advance in the game. Soon those reliances become responsibilities that start to overshadow real life.
Some anime is specifically drawn and written to take advantage of the type of person that would obsessively envelope themselves into their favorite anime's branding. Do a google image search for otaku, and you will immediately see the kind of profits people peddling 50 different editions of the same figurine must be raking in.
Take a look a bluelight.ru and erowid. The former is a forum for discussion of psychoactives the latter a index of chemicals and experience reports submitted by users. Instead of the harm reduction espoused, it encourages dangerous behavior in the name of 'sharing research'; which is just ingesting what could be a chemical without much human research and just writing about it. One wouldn't be compelled to put themselves in such a position if it wasn't normalized and encouraged by a community that was warped by a pattern of addictive behavior.
Grouphug.us is another example. Reddit certainly is as well. Facebook, Twitter, Instagram etc all provide that supplemental 'reward' of positive human interaction without the human component. Your brain isn't stupid, when actual human interaction doesn't provide the reward you WANT, it will learn where it can get it. Psychological addiction is quite the beast.