Another peril is getting on with the lovely creative stuff and forgetting your characters have to live somewhere and that the mundane things of life need to be covered (if only briefly. Unless you are a dragon who can incinerate your own rubbish, a bin collection or waste disposal system of some sort is always needed, just to name one example).
A third peril is falling in love with your created world so much, you forget you actually live in this one. (This one is understandable given how grim the news usually is).
The fourth peril is going for one of the two extremes. You go into too much detail with your world building or, conversely, not enough. Finding the happy medium is not always easy. I've had a great deal of fun in exploring things (such as songs that fit my characters) which won't ever appear in my novels or short stories. (Good material for a blog though!).
And to finish I suppose I would name the fifth peril is of reading back the material you've created to help you write your story/know your characters better before writing them or both and it is lovely and clear to you. It's hard to take a dispassionate look at material you are sharing or which is crucial to your story and think well is this clear enough? (The reverse of this, of course, is to spell things out too clearly and come across as patronizing. Hmm... perhaps that last sentence... time to go I think!).