On the plugin settings page, beside each "position" checkbox, there is an error: "Warning: Missing argument 2 for checked()..." This makes it impossible to apply the plugin to any blog pages, rss, etc. Individual posts do show the desired effect by default, but only when visited separately, at the single post's url. Upgrading Wordpress to version 2.8.5 solves the problem, but the Sociable plugin page on Wordpress.org should be updated to reflect more accurate version compatibility.