If you have a WordPress Multisite (or WordPress Network) with the ThreeWP Broadcast plugin and you would like to move your assets on Amazon S3 you certanly have to deal with with one annoying problem.
The problem is, whenever you broadcast a new blog entry on other sites, the copy_attachment() method doesn’t work, no attachments are copied on the broadcasted posts.
This gist has a solution: https://gist.github.com/jbckmn/9652508
With this little hack S3 hosted images are broadcasted correctly.