In a series of pullbacks we've learned that Facebook beacon will be opt-in. First opt-in was actually opt-out. Currently opt-in is "well we could track you in principle, but we're not. Honest" - but still on a per vendor basis. The obvious right way to do opt-in: A big visible switch inside facebook with an easy to see unmistakeable once and for all in or out. But...the basic problem is that Facebook isn't really interested in giving people that option, much preferring to wear people down with per partner settings. It's the same problem with most apps on facebook. You have the privacy options there - but most apps follow a "if you're not cheap, we don't want to deal with you" policy and just won't work if you won't play viral-spam with them.