I can't think of a specific horror movie as an example, but I know that sometimes being a fan of something can put you at a disadvantage while filming it. Look at Daredevil. They got a huge fan of the comic to make it and part of what's wrong with that movie was that he tried to cram far too many issues that he loved into a two-hour film. It was like a cliff notes version of Frank Miller's run on the book.
Granted, that was only one of the many problems with this skid mark of a film, but it was a big one.
Some people feel that Cabin Fever sucked because it was more of a mishmash of influences than a coherent film. Heard the same said about Kill Bill and House of 1000 Corpses. I loved all three of them, so I can't join in the bashing.