<link rev="canonical" href="http://xyz.com" />
pretending that the DiggBar tells Google where the real address is so all the link juice goes to your website, not Digg. But the fact is that the DiggBar's address is http://digg.com/xxxxx and the rel="canonical" does not work across domains, which means the search engine bots will completely ignore the Digg suggestions so the rel=canonical thingy does not work and is put there just to fool you a little bit into thinking they are not stealing your link juice.
Read about how to remove the DiggBar