Once authenticated with your Twitter id, your Twitter avatar and name are displayed on the associated GFC site. You can tweet your new site membership to your followers at the time you join or at any other time via the site members gadget. You'll also be able to tweet about any interesting discussions happening on the joined site without having to leave it.
The good news for site owners who already use Google Friend Connect is you don't have to do anything to enable the Twitter integration; it just works. And if you don't already use GFC, it might be a compelling reason to start. The new integration is a big boon to Google Friend Connect and the site owners who use it, extending their reach throughout their readers' Twitter ecosystems in one fell swoop.
Check out a demo video of the new integration below and let us know what you think.