45% of diggs from registered users now come from the Diggbar, a switch that happened overnight. A full 75% of incoming Facebook Connections are new Digg users, and 30% of all new Digg registrations come through Facebook Connect.

Before we all get too caught up in Twitter (too late), Forbes has a good, brief, profile on the movements that Digg has made outside of buzz machine of Techcrunch. Coincidentally I was actually just looking at their stats earlier this week and surprised to find it had grown so much. It’s close to 40m people a month in the U.S. (Compete data), that’s 1/3 of the size of Facebook and almost double the size of Twitter.

Considering that many of the ideas for monetizing Twitter involve its power to drive traffic to a URL (search ads anyone?), Digg should certainly not be overlooked. For all it’s non-hotness, it is clearly dominating the space of link sharing. StumbleUpon, Yahoo Buzz, and Reddit combined together reach almost Digg’s size, and is also averaging more visits per person (2.7 visits a month) than StumbleUpon (2.3) or Reddit (2.16).

It sounds like a lot of this is thanks to excellent integration with the Facebook ecosystem, an interesting case of using FB for growth outside of their system.