I'd read somewhere that the reason that it was in "development hell" for ages is that Douglas Adams realized that he didn't want a Hollywood studio working on it and wrote what he considered substandard scripts for it so that he could reject them, which was a right he had gotten in the optioning. Apparently, the rights were due to revert to him at some point, but he died before that happened. Of course, I could be wrong about that, or it might have been a big ole fib.