2. Twitter
This year's social-media sweetheart made a splash (literally) when a
Twitter user posted the first photo of the US Airways Flight 1549 evacuation in the Hudson River. A few months later, even more folks were introduced to the microblogging service when actor Ashton Kutcher challenged CNN to see who could get more Twitter followers.
The company made headlines all year long, thanks to account hijackers, tweeting astronauts, White House updates, Iranian election protesters, overly revealing politicians, and Balloon Boy. "Daily Show" host Jon Stewart and Doonesbury creator Gary Trudeau turned Twitter's ubiquity into parodies that begged the question many had begun to ask themselves: Were all five billion of those tweets really necessary?