Yeah, I totally thought of "morning pages"! I came across that idea a couple years ago.
I have always written a lot, but I never did it as religiously as morning pages. I wrote a wiki in 2004 where I keep all my thoughts/notes -- it's about 1000 wiki pages now (probably 2000 without deletions). Before that I kept a diary but it wasn't really for "ideas", more "complaints" :)
Right now I feel like I have enough ideas and it's about execution... but I do think there is something valid to the approach.
It's also similar to what happens when you write down your dreams first thing in the morning (or even during the night if you wake up after them). I tried this when I was 15. My mind was blown.
I started remembering 7 or 8 dreams a night. I would go to sleep for 50 minutes and it would feel like I experienced 8 hours of time in my dream. It was really disorienting (and interesting). I don't remember but I think it took about 2 weeks of writing before that happened.
So this is another example of writing changing your brain. Your brain wants an audience (or more accurately, your subconscious does, and the subconscious is where ideas are generated). If you write down your dreams, you'll start having/remembering more of them. If you write down more ideas, your brain will generate more of them and follow more associations.