It's a canon feature in Ghostbusters that some ghosts are not, in fact, the spirits of the dead. Some of them are left over residue from various emotional things. For example: A seven car pile up that kills a few and traumatized enough of the people there could plausibly spawn both undead ghosts and ones who embody the anguish of the survivors.
It is therefore theoretically possible that if a convention goes bad enough, say DashCon, Las Pegasus, or Rain Furrest 2015, a ghost could have been formed from it.















