API (and details) on the number of times a URL is shared on Facebook, Twitter, Reddit, LinkedIn, Digg, Delicious, StumbleUpon, Pinterest and Google +1.
Basically, it just compares the current document (in this case your website) to the “top” document available in the browser. If your site has been loaded via the DiggBar then the “top” document will be Digg, so they will be different. When those 2 documents are different, it will automatically redirect the entire browser to your website. Done and done.