Publishing is constrained by a tiny number of giant distributors and two major bookstore chains, all of which demand ridiculous terms on the books they carry. Theatrical distribution is controlled by a couple major chains, which shaft the production companies at every turn. And everyone knows about the payola and other rip-offs that the highly consolidated radio industry visits upon the record labels that want to get their music aired.
In the aftermarket, it's even worse: A heavy concentration in big-box stores lets firms like Wal-Mart tell studios how to re-cut their movies and record companies what to bleep out of their CDs.
So hell yeah, I sympathize with companies and creators who want to keep Google or Amazon from becoming gatekeepers on culture. Not because of who runs Amazon or Google -- I know senior people at both companies whom I believe to be honorable and decent -- but because no one should be that gatekeeper.
I'd oppose consolidation in distribution and sales channels, even if the companies involved were Santa Claus Inc., Mahatma Gandhi Ltd., and Toothfairy Enterprises LLC.