note: i *still* think Facebook should have have stuck to their "Beacon is opt-out" guns, but they also should rollout a universal Beacon opt-out -- if only to satisfy the whiners & privacy geeks (UPDATE: they just announced this, courtesy of Zuck himself.. along with the requisite 'i'm really really sorry'. Beacon univeral opt-out screenshot by Todd Sawicki. good moves both). it probably won't get adopted by more than 2% of audience, but it's a much better way to go than suggesting Beacon is opt-in when it really isn't.
the big PR mistake was that Facebook caved on opt-in (or tried to) when they really didn't need to. opt-out isn't a cardinal sin, and opt-in isn't holy... but trying to position yourself as opt-in when you're still mostly opt-out was probably not the right call. and that's the PR issue they're dealing with right now, not that opt-out was the default.
JUST CAUSE IT'S OPT-OUT DOESN'T MEAN YOU DON'T HAVE PRIVACY CONTROL.
here's the net-net on opt-out vs opt-in -- whichever default setting you choose, you should realize that 90% of userbase (or more) is never going to change that setting. so if you're Facebook the real question is: do you want 90% of your users to use Beacon, or 90% of your users to NOT use Beacon? i think the answer is pretty obvious. ultimately, News Feed / Beacon isn't very useful for anyone (Facebook, users, advertisers) if a) there isn't enough story inventory, and b) if people aren't clicking on the stories. while b) may still be up for discussion, if Beacon isn't opt-out then a) is dead in the water from the get-go.
now certainly you DO need to provide privacy tools & management for people to manage what they do and don't want other people to see... but those tools are already available on Facebook privacy settings
(except for the universal Beacon opt-out, currently). if i don't want stuff to be published, i just change the settings on what kind of data & stories are displayed. or, on a case-by-case basis, i can hide stories in the Mini-Feed that i don't want people to see.
people who are going bananas over Beacon should understand that most people on Facebook are used to the default being opt-out (ie, lifestyle transparency), not opt-in (selective sharing).
that may not work for some folks and that's fine -- as with abortion:
don't like it? don't have one.
fact of the matter: most of this shit just doesn't matter to most FB users. it might be a PR screwup, but as long as the userbase doesn't have a negative reaction, eventually the advertisers won't give a damn.