Just recently, a group of people on the website deviantART were effected by Tulpas that were created as a result of intense stalking and paranoia sparked by a user named "ReturnToUs". The events that took place were eerie, and I experienced them first hand. I will not state my username here, but the people involved were "Mesocyclonegirl", "I-Sunny-I", "TheMask02", as well as a few others I can't remember or didn't meet. There were a number of "proxy" accounts like ReturnToUs that tormented the "marked" "players" of "the Game". There were a number of "unmarked" who were insistent on ending the game. I will not mention their names here.
As the "game" progressed and grew more intense, signs of tulpa creation became evident. Mesocyclonegirl was the first to show symptoms, telling stories of attacks from proxies and random visits from "him", as well as possible threats and visits from the Novus Ordo Europa.
I-Sunny-I was the first to break. Her personality changed dramatically, and she began alienating herself from friends and people trying to help her. She deactivated her account for some time and created a new one under the name of "ipityyou-b-l-I-n-d". She created youtube videos that sparked further belief in "him" and inevitably fed her Tulpa with those activities. She also made a twitter account, @sunnyislost. She realized what she was doing and snapped out of it, deactivating all related accounts and hiding all of her YouTube videos. She created a new account on deviantART under the name "HaretaYoru" where she presented her tulpa theory. She has since re-activated her main account and is continuing her life as if nothing happened, presumably hoping it will keep her tulpa at bay.
All involved members of the "game" who had developed a tulpa were notified, and they were able to at least stop the effects of the Tulpas with this knowledge. The game ended. ReturnToUs stopped contacting people. ReturnToUs had been cultivating Tulpas, creating them on purpose.
There are rumors that more people might be targeted on that site again. Artists are more open-minded to this kind of thing.
For now, things are quiet.