Just read the permaculture article featured in Hobby Farms, Jan/Feb 2010, and it brings up the fact that many new permaculturalists are conventional farmers who are making the shift. Especially in large scale circumstances, even with polyculture, he has been able to utilize his large machinery, and thinks this is a good thing as we still need to provide food for the masses. It sounds like he has a pretty nice operation going--forest farm style.
Yes, it is great what is happening on a broad scale in Permaculture. Often (especially in Australia), this broadscale Permaculture goes by other names like holistic management, pasture cropping, keyline farming etc. etc.
Even simple polycultures in broadscale ag are a great improvement on current systems.
Check out Darren Doherty et. al's RegenAg(R) work:
Darren is indeed the man - when it comes to experience in setting up large scale systems that generate income for people, families, even regions, noone come even close to matching him. I don't think anyone else in the world can say that he's probably generated in excess of a billion dollars in revenue for his clients !