On the dissatisfaction of profits, I seem to recall a conversation when Duke Leto was going over the spice production accounting books, and he saw that there was a whole lot of waste, bribing, siphoning off of money, that kind of thing; about it being run really, really poorly.

On your first point, I thought what they were saying (about not being able to refuse the Emperor's order) was something along the lines of, "Technically, the Emperor has the authority to order us there." It seemed that, as a practical matter, houses always had a second option-- flee into exile. I think Paul's question wasn't, "Why don't we just say no?" I think his question was, "Why don't we make a plan to fight, or make a plan to flee?"

But, as I freely admit, I know hardly anything of the Dune universe. Maybe I should get Smack in on this thread. He's read all the books...