The img.src trick is used by google-analytics to log metrics cross-domain as well. Pretty neat trick.

Another thing to note is the "RESTful" nature of the links embed in the page. I guess its some form of HMAC with SHA1 + Nonce that authenticates requests for the server. It differs for every href. Elegant.

  auth=311110b7ef0f268cafa8616afcbfcec8d977111e