Walt Mossberg is far from alone in giving up on Facebook. But as a leading technology journalist who has spent decades chronicling the impact of Silicon Valley’s policies, his exit from the social network speaks louder than most.

Mr. Mossberg, a veteran of The Wall Street Journal, The Verge and Recode, said on Monday he would be deactivating his Facebook account, along with the Facebook-owned Messenger and Instagram apps.

“I am doing this — after being on Facebook for nearly 12 years — because my own values and the policies and actions of Facebook have diverged to the point where I’m no longer comfortable here,” he wrote on Facebook.

While Mr. Mossberg didn’t list any specific complaints on Monday, his history of public writing left little doubt that his ire was aimed largely at the company’s policies and actions on user privacy. He declined to comment when reached by email.