Social media has grown up. News that breaks on Twitter is now news that moves the markets, sometimes even when it's not news.
Earlier this week, the AP's Twitter account was hacked and a fake tweet was posted about President Obama being injured in an explosion. The Dow dropped 143 points and $136.5 billion in value was shaved off the S&P for a brief period. While the market quickly rebounded, it was a wake up call for investors.
Here's a look at some tweets that affected trading.
By Cadie Thompson
Updated 25 April 2013
Fashion critic Nina Garcia sent JC Penney shares up last July when she posted the following message on her Twitter account:
"I'm @jcpenney's HQ. Thank you Ron Johson [sic] for the walk through of JCP's prototype. Get ready to shop! Its [sic] going to be a game changer!"@ninagarcia )
Even though Garcia had been named JC Penney's "style voice" a month before her tweet, the stock still popped 8 percent.
(Read More: Tweets Moving Stocks)
Last month, shares of the electric carmaker Tesla jumped after its CEO posted a mysterious tweet.
"Really exciting @TeslaMotors announcement coming on Thursday. Am going to put my money where my mouth is in v major way," Elon Musk said.
Shares increased to $38.40 shortly after the post and closed up 2.4 percent to $37.51.
The announcement, delayed until April 2, involved a financing plan in which consumers could lease a luxury Tesla S for an "effective monthly cost" of $500 a month.
Stocks briefly nose-dived Tuesday after a fake tweet on The Associated Press twitter feed said President Barack Obama had been injured in two explosions at the White House. It was quickly confirmed to be fake.
(Read More: This Is the Worst Thing About Fake-Tweet Stock Dive )
The Dow Jones Industrial Average dropped 143 points but recovered within minutes. The false message also triggered a plunge in the S&P, briefly shaving off $136.5 billion of the index's value.
In August 2012, a fake Twitter account of the Russian minister of Internal Affairs, Vladimir Kolokoltsev, sent out three tweets claiming that the president of Syria had been killed.
The news sent the price of sweet crude up more than $1 to almost $92.
"ATTENTION. RUSSIAN AMBASSADOR IN DAMASCUS REPORTS THAT PRESIDENT OF ARAB REPUBLIC OF SYRIA BASHAR AL ASSAD HAS BEEN KILLED OR INJURED." (@MiniInterRussia)
ACCORDING TO UNCONFIRMED REPORT FROM RUSSIAN DIPLOMATS IN DAMASCUS PRESIDENT ASSAD HAS BEEN KILLED TODAY. (@MiniInterRussia)
RUSSIAN GOVERNMENT CONFIRMS: BASHAR AL ASSAD, PRESIDENT OF SYRIA, HAS BEEN KILLED TODAY IN LATAKYJA WITH HIS WIFE AND TWO PEOPLE. (@MiniInterRussia)
The bogus account later took down the bogus tweets.
Hedge fund manager Doug Kass may have affected Apple's stock when he sent a tweet in February—one day before the company's shareholder meeting—that Apple might announce a stock split.
"High above the Alps my Gnome is hearing a rumor that Apple will announce a stock split at tomorrow's shareholder meeting. $AAPL," Kass tweeted.
Shortly following the post, Apple shares rose 1.2 percent to $448.04 after hitting an intraday low of $437.66.
Kass later tweeted that he was selling off some of his "outsized position" as the "rumor seems to be baseless."
Pimco founder Bill Gross predicted via Twitter in 2011 that the Federal Reserve might hint at another round of monetary stimulus at its annual symposium in Jackson Hole, Wyo.
"Next Jackson Hole in August will likely hint at QE3/interest rate caps," the tweet said.
The Dow jumped on the news, and the tweet was later removed.
In April, Jeff Gundlach, founder and CEO of Doubleline Capital, shared some of his market views at a luncheon he hosted in New York City.
"NEW GUNDLACH SHORT IDEA: CHIPOTLE. 'Gourmet Burito is an oxymoron.' Was saving it for Ira Sohn but couldn't resist mentioning. $CMG"
The restaurant's stock dipped more than 2 percent after Gundlach's comments.
Audience, a company that makes voice processors, saw a 25 percent drop in its stock price after a false report surfaced on Twitter that the company was being investigated for fraud.
"Audience noise suppression company being investigated by DOJ on rumored fraud charges Full report [sic] to follow later," the tweet said. It was posted by an account with a handle that appeared to be from Muddy Waters' founder Carson Black, but the account was a fake.
Muddy Waters later sent a real tweet: "There is NO report. This is a hoax. MW does not know this company."