According to SimilarWeb, in April, total Facebook visits (both to Facebook.com and through its mobile apps) fell from 24 billion in March, down to 22.77 billion in April — a drop of 1.3 billion visits, and down 5.15% of the total.
Assuming the average Facebook user visits the social network once a day, that would suggest an average of about 43 million less users during that month. In recent months, Facebook makes about $5 per user, per month — i.e. some $215 million in potential lost revenue.[source]