On Dec 13, 2011 AddThis, a sharing platform, and Clearspring, a social data aggregator, presented the sharing trends of 2011. AddThis is used by more than 11 million sites, which gives it aggregate sharing data for more than 1.2 billion users.
Here is some data according to AddThis Analytics:

• Facebook accounts for 52.1% of sharing.
• Twitter was up 577% this year and accounts for 13.5% of sharing.
• Tumblr sharing has grown over 1299.5%, and is accelerating.
• Digg and MySpace didn't do so well in 2011. Their sharing rates continued to fall (47.7% decline for Digg and 56.9% decline for MySpace.)

Check more bits of statistics at http://www.soldlab.com/content/readMore1/infobox/featured_news/template/default/active_id/5