IMDB's daily traffic from Facebook has doubled since integrating the 'Like' button

"More than 100,000 sites have already integrated social plugins. Across various industries, people have shown that they want to interact and share and see what their friends recommend. We are excited to report some early results that website developers have shared with us:
News: News sites have implemented social plugins to help surface individualized content for readers, and in the process seen significant increases in daily referral traffic from Facebook. For instance, Facebook referral traffic increased by 250% for ABC News and 80% for The Globe and Mail, Canada's largest-circulation national newspaper. The Globe and Mail has also found that people who have liked their Facebook Page are more engaged on their site — and comment, share, and read more.
Movies & Video: IMDb.com has seen daily referral traffic from Facebook double, and its users have generated more than 350,000 likes. Dailymotion, one of the top 50 most-trafficked websites in the world, has seen users click the Like button tens of thousands of times per day on their site. As an example, more than 250,000 users have engaged with one of the most popular videos on Dailymotion, PIXELS by Patrick Jean, and a quarter of its views are from Facebook users.
Sports: NHL.com, the official website of the National Hockey League, has seen an 80% increase in referral traffic from Facebook, as people interact with articles, scores and videos.
Publishing: Scribd, a site that helps authors publish their writing, has seen their referral traffic from Facebook double as authors gain followers among groups of Facebook friends."
Source: Facebook Developers blog, 11th May 2010