Jan. 13: "dead bodies are everywhere i havent seen one ambulance or any proffesionl med care anywhere in port-au-prince."
— Frédéric Dupoux
The earliest reports and photos of the Haitian quake come via Twitter and Facebook, including this one from a freelance photographer in Port-au-Prince.

Jan. 22: "Hello Twitterverse! We r now LIVE tweeting from the International Space Station — the 1st live tweet from Space! :) More soon, send your ?"
— NASA astronaut T.J. Creamer
The first live tweet from the great beyond.

Feb. 4: "This tweet sent from an iPad. Does it look cool?"
— Wall Street Journal exec Alan Murray
Oops! Premature expostulation! Nobody was supposed to know the iPad was out yet.

June 9: "@Snooki u r right, I would never tax your tanning bed! Pres Obama's tax/ spend policy is quite The Situation! but I do rec wearing sunscreen!"
— Sen. John McCain (R., Ariz.)
After Nicole "Snooki" Polizzi of Jersey Shore complains about an Obama plan to tax tanning salons, candidate McCain sympathizes. Snooki's memorable response: "Haha Yes!!"

June 21: "Rolling Stone quotes Gen McChrystal says Amb(ret Gen) Eikenberry 'betrayed' him with leaked memo last yr doubting Karzai story is out fri"
— Andrea Mitchell, NBC chief foreign-affairs correspondent
The tweet leads reporters to Rolling Stone's incendiary article about Gen. Stanley McChrystal, chief commander of U.S. and NATO forces in Afghanistan. He is relieved of his command two days later.

July 18: "Ground Zero Mosque supporters: doesn't it stab you in the heart, as it does ours throughout the heartland? Peaceful Muslims, pls refudiate"
— Sarah Palin
Told there's no such word as refudiate, Palin tries again using refute, then comes out swinging: " 'Refudiate,' 'misunderestimate,' 'wee-wee'd up.' English is a living language. Shakespeare liked to coin new words too. Got to celebrate it!" The editors of the New Oxford American Dictionary choose refudiate as their word of the year.

Sept. 1: "Police situation at the Discovery building in Silver Spring. Surrounding buildings being told to remain inside."
— @FixWMATA
When a gunman takes hostages at a Discovery Channel building in Silver Spring, Md., on-the-scene tweeters post the first reports.

Sept. 14: "Gay Veterans were my VMA dates. Repeal Don't Ask Don't Tell. CALL HARRY REID to Schedule Senate Vote."
— Lady Gaga
Pressing Sen. Harry Reid (D., Nev.) to set a vote on "Don't Ask," Lady G sends this message, and a picture of herself and service members attending the Video Music Awards, to six million Twitter followers. Reid, who's running for re-election, tweets her back and schedules the vote.

Sept. 17: "Regrettably, I did in fact fail my most recent drug test and if I am asked, I am prepared to appear before Judge Fox next week as a result."
— Lindsay Lohan
LiLo announces she has failed another drug test. She is in for a round of court dates, jail time, and rehab.

Oct. 24: "WE DID!"
— Katy Perry and Russell Brand
The U.S. pop singer and Brit funny-guy announce their marriage.

Nov. 9: "I can't be everybody's hero and villain savior and sinner Christian and anti Christ!"
— Kanye West
In a spectacular series of rants on Twitter, West tells why he has refused to perform on NBC's Today.

Nov. 16: "The Prince of Wales is delighted to announce the engagement of Prince William to Miss Catherine Middleton."
— @Clarence House
The most romantic tweet of the year, from the official Twitter royal account.

Dec. 1: "In Gus' Restaurant on Rt 33 in Manalapan having lunch. One of NJ's great diners. Meeting lots of New Jerseyans in the holiday spirit."
— N.J. Gov. Christie
The Garden State governor shows he is a past master of social media.

Dec. 1: "WikiLeaks servers at Amazon ousted. Free speech the land of the free--fine our $ are now spent to employ people in Europe."
— @WikiLeaks
As Amazon and other suppliers cut ties with WikiLeaks, the website sends out blow-by-blow tweets.