PALO ALTO: Facebook has bowed to pressure from tens of thousands of users and modified its Beacon advertising system that circulates purchasing information among 'friends'.

The 55 million users of the online social networking site will be given greater control over whether to participate in Beacon when they shop on partner websites; and will have to explicitly opt-in before any information is passed on.

Members complained that the system's initial incarnation made opt-out boxes hard to find, while many were unhappy about breaches of privacy.

Data sourced from Business Week (online) and Associated Press; additional content by WARC staff