I have seen some blog sites that includes a bar of such sites icons like: Digg, Del.icio.us, Fark, Blinkbits and Fark etc.
Is this really good to place these website icons to promote your content?
Does it really help SEO to increase traffic and to make your link popular?
Secondly, If someone has already Digg the blog_post and if again someone other tries to Digg the same blog_post. Will the same blog_post be added for twice or it will just make the existing link popular?