Big announcement.

Biz Stone, co-founder of Twitter, is joining The Huffington Post Media Group and AOL as Strategic Impact Adviser. Said Mr. Stone: “The definition of success is changing as we begin to understand the value of helping others. Arianna and Tim share my vision for aligning corporate resources toward meaningful change,” said Biz Stone. “My goal in partnering with AOL and The Huffington Post Media Group is ambitious but vitally important. Together we will rally companies to think about new ways of doing business, share best practices, and strive for positive impact at all levels — from global to local.” Mr. Stone will advise on social impact and cause-based initiatives, develop a platform to facilitate people doing service in their communities, rally other companies to invest in and deploy best corporate practices, and create and develop a video series spotlighting leading companies and executives at the forefront of philanthropy and corporate responsibility.

As far as I can tell this is purely advisory – Stone (@biz) hasn’t left Twitter – but this is still an interesting move, especially on the back of the recent AOL acquisition of The Huffington Post. And for Biz, fingers in lots of pies, and all that. Worth keeping an eye on.