Facebook's "I Like" Button Opens Surveillance
The "I Like" button popping up on commercial and news organizations' websites violate basic privacy rights of online users, such as, no secret data collection, opt-in to the sharing of personal information, and the right to know who has accessed or used their personal information. When online content users select the button--Facebook tracks both Facebook and non-Facebook users' online activity. Tracking is not limited to the site where users clicked the "I Like" button. Better, richer, and more detailed profiles of online users' activities feeds the demand for more detailed customer profiles to sell advertiser and marketers.
Facebook 'Like' button draws privacy scrutiny, by Declan McCullagh