There's also the whole 'Sony can't reach over the air or through Sony Ebook Library and start deleting titles off my reader' issue that Amazon's already invoked once. Even APPLE has been careful about not using the killswitch on any apps they currently offer in the app store - they'll just remove it from the listings, which means you can't get it... and that's it. Knowing Amazon can, and is more than willing, to go into your Kindle to start deleting books is.. well, it's a good incentive to not go Kindle.
Of course, for extra irony points, they had to start this practice with 1984..