Facebook Beacon was the advertising system introduced in 2007 that shared users’ activity from partner websites with their Facebook friends.
Beacon was announced in November 2007 as part of Facebook’s advertising strategy. When users bought or interacted with products on participating external sites, the system could send information about those actions to Facebook, where it could appear in social stories.
The program quickly drew criticism because many users felt they had not clearly consented to the sharing of their activities. Privacy objections led Facebook to change the system, and Beacon was eventually discontinued.
Beacon is distinct from later Facebook advertising products such as Atlas and Audience Network. It was notable not simply for targeted advertising, but for attempting to turn off-site consumer activity into visible social recommendations.