Americans who use Twitter are more likely than the average adult to be highly active on the Internet and in their communities, according to new survey by Gfk MRI. The survey found people who use Twitter are highly active when it comes to blogging, video sharing and posting reviews. They are 506% more likely than the average U.S. adult to write a blog, 451% more likely to upload or add video to a Web site, and 314% more likely to post a comment or review on a blog,