I saw the clip from BBC News tech program ”Click” about facebook security and was kinda surprised about what they did.
For those who’ve been living under a rock or on the moon or something the last period of time, Facebook is a social networking site – “Web 2.0” buzzwords and all – where people share all sorts of things about themselves. Like so many other similar sites.
I use it marginally myself (link in right hand column), mostly because I’m terrible at keeping in touch with people, so having them “collected” in some service is handy 
Anyways, on Facebook you can play all sorts of mini-games and take all sorts of quizzes and people can develop these third party applications for others to utilize.
What BBC did in Click was make an application which could take all the private data you have on your profile and send it to the developers of said application. Now, this is bad enough in itself, but worse – you didn’t even have to use the application yourself, but it would apparently be enough if one of your friends did so, as it could lift data from the friend list.
Now personally I’m a type which drifts between complete paranoia and complete trust 
If I trust a site, I have few qualms about sharing a number of private information, if not – I’ll keep a tight lib about most actual information. But I’m also extremely careful what I install and run and accept – hence I do not fear such applications on Facebook if only I had to run them myself, cause chances are slim that I would anyway.
But if I’m suddenly dependant on my friends not running all sorts of small applications in their facebook time, the danger factor multiplies. Not because I think my friends would run such applications and simply run anything they get their way – but simply put – more factors, more possibilities.
I hope Facebook is on top of this situation and it quickly will go away due to increased security about our personal data.
Otherwise it only takes one or two larger cases of identity theft on facebook to drive many users away and then the entire buisness plan crumbles.
Personally though, then on top of all this Beacon information sharing, I share next to nothing of consequence on a site such as Facebook which couldn't already be found by searching the web - but I’ve seen many others share much personal information though. It is a dangerous situation waiting to happen lest security is top notch (perhaps it has already happened yet people do not know about it themselves)