Angsuman's Feed Copyrighter Plugin
Unfortunately some people use technology to steal content. The current state of affairs makes it much easier for thieves than those trying to contract thieves. This plugin at least makes it obvious the thieves are intentionally being thieves. Unfortunately that is about all it does.
I would expect over the next few years trusted sources will emerge that categorize thieving domains as such. Then those who wish can have browser plugins that notify them a site they are viewing (or even links they see are to) steal content.
A good post on dealing with thieves: What to do when someone steals your content.