I'm looking for a plugin that offers the social bookmarking features your plugin has while not wasting link benefit (nofollow not an option, it deletes link benefit).
Anyway, noticed you use links but not with href, instead shr_href which is custom code and I'm hoping is not recognised by the likes of Google as a link. Until seeing the shr_href was just about to delete the plugin as a standard text/image link (even with nofollow) wastes link benefit.
Was there some SEO logic behind using shr_href instead of href? Any SEO testing?
Have you considered using something other than a link for the code? Concerned even a malformed A link code will waste link benefit.
If I ever find a plugin that's SEO friendly will recommend to my WordPress SEO theme users and at http://www.google-adsense-templates.co.uk/wordpress-seo-plugins