While using the Google Webmaster Rich Snippets Testing Tool, I came across with a Warning/Error.
Warning: The information will not appear as a rich snippet in search results, because the marked-up content does not appear to be the main focus of the page. More information. (Is this correct? Let us know.)
In order to get pass through that warning, you need to disable pingbacks and trackbacks in your WordPress discussion settings. To disable, go to:
Uncheck Allow link notifications from other blogs (pingbacks and trackbacks.) under Default article settings. Then click save changes.
That should eliminate the problem.