This is an obscure one, but it's causing me grief. WordPress has a built-in mechanism for escaping shortcodes in a post where you want to say something like: "Use the [gallery] shortcode to create a gallery".
Since WordPress will normally interpret the shortcode, you need to escape it in the post editor by doubling the brackets so it reads: "Use the gallery shortcode to create a gallery". Here's the trac entry that added this feature.
Unfortunately Really Simple Facebook Twitter share buttons version 2.6 breaks this mechanism, so WordPress will still interpret escaped shortcodes. I'm guessing it's a bug in the_content filter really_simple_share, which calls do_shortcode on $the_content. I suspect this is causing escaped shortcodes which have already been stripped of the second bracket pair to be interpreted. Is this call really necessary?