Why Is Hollywood Casting Big Stars in Little Parts?

I think you pretty much covered all the possibilities in your blog. (I like reading your blog btw, especially the "What the hell happened" section.)

The only other thing responsible for this I can think of, is that movie star agents keep lobbying producers to put the stars in movies, no matter how small the role is, cause they get provisions out of it. The bigger the star, the bigger the provision. I can't think of anything else.