Let's just see what can be done without Facebook:
You (pessimizer) have listed your email address pessimizer@xxxxxx .
You have an HN comment history.
Your email pops up in google under Arkansas
You commented on a Django topic.
I could infer your set of HN buddies (maybe not including myself now!).
If you use a pseudonym to hide from those - why don't you use a pseudonym as your facebook account??
I haven't listed my email, but I'm pretty sure people could work out who I was and where I lived from my comment history. But I am reasonably happy that the reward of not having to screen all my comments for incriminating info is worth the risk of someone figuring it out.
(edit with an example)
Point taken, and partially agreed with, but the fact that facebook is systematically doing this about every aspect of every individual's life would guarantee that getting better info than you got about me, in a shorter time, would be trivial.
I imagine there are data-mining companies that are crawling the interwebs systematically to collect detailed information.
Facebook is the motherlode of course, no doubt about it.
Read their term http://www.facebook.com/legal/terms they are things like "transferable, sub-licensable, royalty-free, worldwide license to use any IP content that you post on or in connection with Facebook"
As Stallman pointed out in the interview, the scale of the monitoring is on a different level of what you can do manually. No matter how hard you try, you will not know what websites pessimizer has visited, FB got a list of his/her visits on any site that contains a like button (doesn't matter if he/she uses FB).
Beside the scale of information disclosed, that's how it can be used or not. I'm pretty sure I can decide what products are endorsed on my blog, not so much on FB, and if we visit pessimizer site, no one will now. On FB, they could use this information to know pessimizer better. Guilty by association ;)
Probably they have some common heuristics to spot a fake, but those cannot be too clever.
Re: Scale of monitoring
Does this not just make the haystack bigger for the same number of needles?