I checked all and here's the problem.
First of all, the theme is broken!
@badMike, your code is also broken!
Both, Sharedaddy and my plugin has nothing to do with this.
Themes that are outputting sharedaddy in their theme excerpts are most likely using deprecated
get_the_excerpt( $post->ID ) or
the_excerpt() out of the loop (like in your case @badMike).
What they should do is use
the_excerpt() inside the loop, or use
echo has_excerpt( $post->ID ); out of the loop, and manually apply
I might be wrong, but with my tests (replace
the_excerpt() in twentyeleven's
index.php file) all leads to the explanation above.
Sorry, but I'm closing this for the moment.