If Web users’ use of “AddThis” is a measure of how people share media – and Ad Age thinks it is – then Facebook accounts for more than half (52%) of our media-sharing, but “Twitter was up 577% this year” overall (13.5% of sharing) and accounted for 52% of media-sharing in Japan, interestingly. Tumblr came in third overall, at 1,299.5% growth (fastest-growing). Google’s +1 button has plateaued, Ad Age adds, but Google can be happy that its Chrome browser “overtook Firefox last month” (still second to Microsoft’s Internet Explorer). Sharing by mobile phone grew 6x this year, with Occupy Wall Street having caused “a 217% spike in mobile sharing” on October 25. Surprising were the most-shared topics, with Osama bin Laden topping the chart. Kim Kardashian’s divorce didn’t even make the Top 10 (sorry for the sarcasm). Do check out Ad Age’s infographic for the rest of the 10 most-shared topics.