So what did the film makers do to supposedly piss off the spirits? Well, they used real human remains as props in the first Poltergeist movie. You know, the movie about how desecrating the remains of the dead angers their spirits.
What sucks about that is that none of the supposed curse victims were actually involved in the decision to use real human remains on the set. Doesn't it ruin the whole point of a curse when you go inflicting it at random? That's just sloppy.
Most Tenuous Link to the Curse:
According to a noted expert on the film (Read: Wikipedia) JoBeth Williams, who played Diane Freeling, claims she returned home from the set each day to find pictures on her wall askew! She would then straighten them out, only to find them crooked again the next day!
Supernatural or not, it's just shitty curse work when you have to use a laser level to even figure out it's going on.