I do not understand exactly how RSS directories works. What happen when i submit my blog (rss feed of blog) to rss directories ? I have heard that this can generate many backlinks to my blog post? Does they show in their site excerpt of my blog post or full post ? Whenever there could be the duplicate content penalty cause of this.? Or do not? Also does anyone have list of rss feed directories display no content (just title if recent posts such as http://www.rsshugger.com) so there won't be duplicate content penalty? Thanks
Don't worry about a duplicate content penalty. If it's something that something that a competitor could do to your site, it won't get you penalized. Google doesn't want to start a webmaster war with sites all over the web just spending their time sabotaging each other.
Also does they use excerpt directly from post.? So if i made custom excerpt,rss directories still use version from posts ?
I also want to know whether the rss directories like Technorati and others result in duplicate content issue? I have seen some directories appear for my targeted keywords while my blog is nowhere to be seen for those keywords.
Put a 'nofollow' on all of those buttons for external services, such as the 'Favorite Me at Technorati' button. Turn-about is fair play, IMO. They nofollow to your blog, why not give them the same in return?