You land on a page that says, "Verification required. Complete one survey to unlock the viewer." You click the link and are taken to a survey that asks for your name, address, phone number, and credit card info (for "shipping" of a free trial). The scammer sells your data to marketers or uses your credit card for fraudulent charges. No viewer is ever provided.
Instead of using FB private profile viewers, consider these alternatives: fb private profile viewer
: Some sites force you to complete endless "human verification" surveys that never actually reveal any profile data. Legitimate Ways to See Private Content You land on a page that says, "Verification required