One metric for measuring the popularity of a social network is how much content is shared between users. Widget maker AddToAny, whose product for content sites lets readers share stories across multiple social media sites, is reporting that Facebook now dominates sharing, with 24% of shares from its widget consisting of users posting items to Facebook. That beats email (11.1%) and Twitter (10.8%), making the world's largest social net the most popular service for sharing content, too. As Mashable's Adam Ostrow says, "this is undoubtedly welcome news at Facebook, as the site continues to emphasize sharing and readies its own real-time search engine."
If you combine all of its properties, including Delicious, Yahoo Bookmarks, Yahoo Buzz and Yahoo Messenger, Yahoo comes in second on the list, accounting for 14.4% of sharing. MySpace comes in fifth with just 5% of shares, while Digg has 4.4%, and Bebo, 3.1%. Ostrow adds that the demise of email sharing isn't a surprise given that social networking now has more reach than email worldwide.