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!"
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)