These are companies, they work with the law: put terms of use on your content which ban cloaking your identity. When the unique identifier you put in your feeds shows up on the unauthorized profile, you now have evidence not only that they were illegally using your content but also they knew that and were trying to defeat an access control mechanism.

At that point, all of the big content companies are on your side – none of them are going for a “but we really want to use their content without paying for it!” argument – and it further increases the number of people reconsidering their continued use of the site.