Social bookmarking sites allow web surfers to save, catalog, and share interesting pages they find online. The Sociable plugin appends links for your readers to use those sites to the end of each of your blog’s posts, increasing your potential audience.
The reason for this WordPress plugin is in this article: successful-blog-launch. Go to chapter 7 “Social Bookmarking (aka Going Viral)”.
And so I started to look at a wp-plugin that includes all social bookmarking sites (and not for instants only Digg although this is also a very good wp-plugin). And that is the reason I use Sociable.
And now: Stop reading, start promoting my blog….
I know you wanna, just click on one of those little icons on the bottom of the page.