Li Jiang’s journey from village rice fields to a concrete dorm room of snoring men has played out millions of times as migrant workers have reached for a piece of the China dream. That dream evaporated in October for Mr. Li. After a decade in this coastal city, he returned to Fuchang Electronic Technology Co. from a weeklong holiday to find the maker of cellphone bodies and set-top boxes had stopped production, leaving him and five family members jobless. In notices on the factory gate, Fuchang blamed a credit squeeze and its own bad management. With no word on severance, Mr. Li and some 1,000 of Fuchang’s workers took to the streets. The next day, 3,000 protested, workers and labor activists say, fueled by worker anger and social media. “I kept calling people to join,” says 30-year-old Mr. Li. “The more the better to build our strength.” […]