Twitter calls them "hashflags": http://help.twitter.com/entries/186934-what-s-happening-with-the-world-cup http://help.twitter.com/entries/186934-what-s-happen

Twitter calls them "hashflags": http://help.twitter.com/entries/186934-what-s-happening-with-the-world-cup http://help.twitter.com/entries/186934-what-s-happening-with...