Unique visitors to Digg.com reached 17.4 million in August, according to comScore. That kind of U.S. only traffic crushes Digg's competition, including Yahoo's Buzz, which grew a little during the past year, and AOL's Propeller, which tanked.

We don't have Digg's unique visitors from this time last year, because comScore changed the way it measures the site's traffic this past July. Still, a comScore rep says, "Digg is definitely growing strongly."

Why the surge? A Digg rep cites "recent implementations like integration with Facebook Connect, DiggBar launch, Digg Dialoggs and the continued flow of great content submissions from the community."

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