Author John Scalzi's Whatever post here. He also spends several other posts talking about the issue so head over to Whatever and search through them if you want to read them all.
Agent Nathan Bransford expresses his opinion here.
Agent Kristen Nelson here.
Agent Jessica Faust here.
AND it didn't take very long before the comics jumped on the whole affair. The Onion has posted a video poking fun at whole debate in a serious of fake interviews. You can find the link on Galley Cat here.
In the end, it doesn't matter if you're for Team Amazon or Team Macmillan, it seems to me that the people getting hurt by all this posturing is the authors themselves. Without the "buy" buttons activated on Amazon, it's the authors who miss out on sales and authors today can least afford to bear the brunt of this issue. I buy all my books from Barnes and Nobles and there are plenty of other places to buy your favorite author's books. So make sure, a deactivated "buy" button on Amazon doesn't stop you from going to the next site to buy a book. Your favorite author will thank you.