Digg will be the first partner / user of Facebook Connect.

Quoted: It will allow users to “connect” their Facebook identity, friends and privacy to any website. Third party websites will be able to implement and offer more features of the Facebook Platform off of Facebook – the same features available to third party applications today on Facebook.
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To make data portable, Facebook believes it’s about giving users the ability to take their identity and friends with them around the Web, while being able to trust that their information is always up to date and always protected by their privacy settings. The next iteration will be available publicly within the next several weeks.
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One of their initial launch partners will be Digg.