Joen Asmussen

This plugin appends a customizable message with a link to every post in your RSS feed. This can help discourage robots from scraping your content (automatically copying and posting it elsewhere). This is the default message:
<pre><code>[postname] originally appeared on [sitename] on [postdate].
</code></pre>

Anti Feed-Scraper Message

Discourage robots from scraping your RSS feed.

ringmaster

This plugin performs the simple task of replacing individual author names in feeds with the site name.
This is useful for blogs that are written by multiple authors that have the “authoritative voice” of the blog itself, 
rather than attributing each post to its individual author. This plugin makes the posts in the feeds (all feeds: rss, 
rss2, atom, rdf, etc) appear to be written anonymously, instead using the name of the site as the publishing author, 
rather than the name of the author. This prevents admins from having to edit core files to make posts in the feed anonymous.

Feed Anonymizer

Replaces individual author names in feeds with the site name.

Anti Feed-Scraper Message vs Feed Anonymizer