Since Facebook introduced the new Beacon ad system earlier this month, more than 50,000 Facebook members had signed a petition objecting to the programme, which sends messages to users' friends about what they are buying on various websites, including and Blockbuster.
Late yesterday Facebook made an important change, saying that it would not send messages about users' internet activities without getting explicit approval each time.
The company said in a statement: "We appreciate feedback from all Facebook users and made some changes to Beacon in the past day. Users now have more control over the stories that get published to their mini feed and potentially to their friends' news feeds."
Users now have to proactively consent to Facebook posting their actions onto their news feeds by clicking an "OK" button, which pops up once a consumer makes a purchase on participating websites.
If the user does not act, the notification will go away until a future Beacon pop-up appears -- it will contain all older, unapproved notifications as well as the new one.
has also expanded the user help section that deals with Beacon, and links to it on every pop-up notification for the programme.
The release said: "We recognize that users need to clearly understand Beacon before they first have a story published, and we will continue to refine this approach to give users choice."
Political group started the anti-Beacon petition on November 20, complaining the Beacon system was an intrusion of privacy. As of last night more than 50,000 Facebook users had signed it.
There is still no way to universally opt out of participation in the Beacon program. MoveOn.org said it would be tracking the effects of the latest changes before deciding if it would still push for a universal opt-out.