John Biggs of the New York Times (through Bend Bulletin) presented the facts:
In October 2010, Noah Kravitz, a writer who lives in Oakland, Calif., quit his job at a popular mobile phone site, Phonedog.com, after nearly four years. The site has two parts — an e-commerce wing, which sells phones, and a blog.
While at the company, Kravitz, 38, began writing on Twitter under the name Phonedog_Noah, and over time, had amassed 17,000 followers. When he left, he said, PhoneDog told him he could keep his Twitter account in exchange for posting occasionally.
The company asked him to “tweet on their behalf from time to time and I said sure, as we were parting on good terms,” Kravitz said by telephone.
And so he began writing as NoahKravitz, keeping all his followers under that new handle. But eight months after Kravitz left the company, PhoneDog sued, saying the Twitter list was a customer list, and seeking damages of $2.50 a month per follower for eight months, for a total of $340,000.
PhoneDog Media declined to comment for this article except for this statement: “The costs and resources invested by PhoneDog Media into growing its followers, fans and general brand awareness through social media are substantial and are considered property of PhoneDog Media LLC. We intend to aggressively protect our customer lists and confidential information, intellectual property, trademark and brands.”
One notes that the Twitter account was created while Kravitz was an employee and the account name included the text "Phonedog." Customer lists are something that can be protected under the rubric of "trade secret," but they have to be a secret, and not revealable. In the future, accounts started after employment begins and trading on the company brand, should be explicitly covered in an employment agreement. An account started before employment began, not utilizing the tradename of the employer, would present a different situation.
See also Who gets custody of Twitter when an employee quits?