Dare has some great thoughts on the Facebook Beacon issue. Realize that he’s working for Microsoft, who is both competing with, and investing in Facebook (though he blogs for himself and not the company). Disclosure – as a former MSFT employee, I have some investment there.
No global opt-out: There is no way to turn off this feature. The best you get is that when a site tries to publish an update to your news feed and mini-feed, you get an entry for the site added to your Privacy Settings for External Websites page on Facebook. I guess it never occured to Mark Zuckerburg and Justin Rosenstein that not sharing my purchase history with Facebook is a valid privacy option. Why do I have to police this list and refer back to it every couple of days to figure out if some new Web site is now publishing my private data to Facebook without my permission?