From Henrik Torstenssons Weblog: 'Facebook's Beacon program, where Facebook's partner sites automatically report your activity on their sites to your Facebook account, doesn't pass my smell test. What Facebook has built in Beacon is spyware. If Facebook doesn't redesign Beacon, making it opt-in and far more transparent than today, I will be very surprised if this doesn't lead to either a member backlash or regulation by lawmakers.
An example of how Beacon works: Click on Play Now and Joost will report your action to Facebook and unless you actively say no, your activity will end up in your newsfeed.'
More food for thought on the same issue from Ethan Zuckerman, "Facebook changes the norms for web purchasing and privacy", and from David Weinberger, "Facebook's privacy default" (via Rebecca MacKinnon)