At the top of Twitter's 'The 10 Most Powerful Tweets of 2010' list, when a Doctors Without Borders plane could not get clearance to land in earthquake-ravaged Haiti, reporter Ann Curry tweeted: @usairforce find a way to let Doctors without Borders planes land in Haiti: http://bit.ly/8hYZOK THE most effective at this. She convinced the US Air Force to let the plane land. A woman walks by a pile of rubble on the streets of Port-au-Prince, Haiti, on Jan. 16.

Mary Knox Merrill/The Christian Science Monitor