In an op-ed published in The Wall Street Journal on Thursday evening, Zuckerberg set out to explain "The Facts About Facebook" and, in particular, the facts about one of the most contentious elements of the platform: advertising and data privacy... On the principle of ad targeting, Zuckerberg writes that users want ads to be relevant, and to do this Facebook needs to "understand their interests" -- but ultimately, users have transparency and control over how their information is used... Zuckerberg acknowledges the "complexity" of the company's advertising model has led to yet more concerns, including whether Facebook sells user data or deliberately allows controversial content to remain on the site in order to "increase engagement."