  Users disclose ever-increasing amounts of personal data on Social Network
Service platforms (SNS). Unless SNSs' policies are privacy friendly, this
leaves them vulnerable to privacy risks because they ignore the privacy
policies. Designers and regulators have pushed for shorter, simpler and more
prominent privacy policies, however the evidence that transparent policies
increase informed consent is lacking. To answer this question, we conducted an
online experiment with 214 regular Facebook users asked to join a fictitious
SNS. We experimentally manipulated the privacy-friendliness of SNS's policy and
varied threats of secondary data use and data visibility. Half of our
participants incorrectly recalled even the most formally "perfect" and
easy-to-read privacy policies. Mostly, users recalled policies as more privacy
friendly than they were. Moreover, participants self-censored their disclosures
when aware that visibility threats were present, but were less sensitive to
threats of secondary data use. We present design recommendations to increase
informed consent.
