People assume that writers steal ideas from other people. But in my experience, what's much more common is coming up with what you think is an original idea and then having the horrible expereince of watching a movie/TV show, or reading a book where exactly the same thing happens.
For example, I was watching the fantastic Paul Verhoven flick Black Book on DVD a couple of nights ago and thinking what a magnificent performace Clarice van Houten gave as the lead character - and wouldn't she be great as the heroine if they ever actually filmed my book: this is what James Twining calls 'casturbation' - when it suddenly struck me that there's a really significant plot/characterisation line in Black Book that is absolutely identical to the central emotional theme in the book I've just started.
Since my book has already had to be totally re-planned once, after at least half-a-dozen elements of my original plot appeared in the last series of 24, this is (to put it mildly) effing annoying.
So am I the only one who drives his family nuts because I can't watch a film without seeing if it has similarities to something I have written, or am writing?
Or are we all equally paranoid?