The information about their business model and data practices which people seem to be so surprised by was/is common knowledge among people who work with these technology stacks. Going to work for Facebook seemed like it would have meant supporting and abetting those practices; they were very clear about what they were doing, and the roles were in no way ambiguous.
The cynic in me wonders if these employees are just responding to how others are starting to view their positions, more than ethical or moral quandaries.