(Photo: NJ Governor's Office/Tim Larsen)

Twitter, Tumblr and Pinterest were hacked this week, after a security breach at customer-service provider Zendesk allowed a hacker to access user email addresses at the three social media companies. [Wired]

Facebook COO Sheryl Sandberg's book marketing plans include "Lean in Circles," in which women study Ms. Sandberg's curriculum for career success. [NYT]

Twitter cofounder Ev Williams talks about when—and when not—to sell your company. [Medium]

Nevada became the first state to legalize online gambling. New Jersey Gov. Chris Christie may sign a law legalizing Internet gambling in his state as early as next week. [The Washington Post]

If you're a "startup junky," what are you really addicted to? [PandoDaily]