Fair cop(yright), guv?

An interesting courtroom case is getting underway at the moment. Dan Brown's book The Da Vinci Code (buy it here) has been accused of stealing the main ideas or 'architecture' of another book, albeit a 'non-fiction' work.

Plagiarism is one of many thorns in my side at work, but a broader legal definition is probably not the answer. Ideas of copying intellectual 'architecture' would certainly broaden its scope. For instance, last night I watched Happiness Of The Katakuris (2003 - buy the DVD here). If I put pen to paper on a guesthouse zombie musical claymation novel tomorrow, am I ripping off said film directly, or merely borrowing from its overall structure? How do you tell these procedures apart, and which - if any - are legitimate?

We all know it's possible to make money from ideas, but could this case set precedents, enabling the idea of intellectual property rights to stifle much more than just the impending movie? Time will tell...