The letter also asks for general background info, such as the number of data policy violations from the past 10 years, privacy assessments since the FTC decree from 2011, as well as the number of apps Facebook audited. The collection took place through an app, "thisisyourdigitallife," that gathered information about both its immediate users and their Facebook friends.

Wyden has given Zuckerberg until April 13th to provide answers.

This isn't the same as a formal investigation, and won't necessarily lead to action. Members of Congress have a habit of sending letters whenever they're concerned about a subject, and only occasionally follow up -- it's frequently about the public show of concern more than tangible action. This shows that the issue is alarming enough to at least draw attention from Congress, however, and Wyden is on the Senate Intelligence Committee. It won't be surprising if this leads to a more substantial investigation, especially in light of concerns about election manipulation.