Providing social bookmarking buttons can be a service to your visitors, and help highlight your best content on various social networks and news services, but you must think carefully about which ones you include, and where.
How many blogs link to Technorati on every post they publish? Many blogs also use followable links to social bookmarking sites such as Delicious, and social news sites such as Digg on every single page of their site? Google in their recently disclosed patent are saying that it could be a negative indication of quality.
Neil Patel has been discussing Del.icio.us today
What he forgot to mention was the Del.icio.us tagometers that were recently introduced by Delicious that you can also add to your blog. I have been testing them on a few niche blogs, and they have proven to be quite effective in encouraging additional clicks.