AP - When Twitter turned five years old on March 21, co-founder Isaac "Biz" Stone was on the road celebrating with some of the popular short messaging service's famous users. In the past two weeks, he has appeared on the shows of Conan O'Brien, Howard Stern and Martha Stewart among others. He also made a special stop in Chicago just to take out Twitter's employees there for drinks — a pastime he calls "beersonbiz."More...