I don't think it's fair to say a lack of anonymity or other mistakes are killing Facebook. It very may well be true that mistakes killed the experience for you, but the truth is that most people are not overly concerned with the lack of privacy on their social networks.
I think people online often mistake a vocal minority pushing for privacy settings on this network as a reflection of the wishes of everyone. Truth be told, most people are indifferent to the matter.
Speaking for my own use-case, it's a mix of founder's statements (http://gawker.com/5636765/facebook-ceo-admits-to-calling-use...), investments by less-than-pristine Russian businessmen, my own various intersections with data mining, personal information aggregators, and legal processes, history of wide-spread domestic spying (watch "The Lives of Others" about the East German Stasi for a chilling view, understanding that this has and does happen in many lands).
The conceivable downsides of open participation in Facebook far outweigh the positives.
Add in social fatigue in the mass market as well, I suspect the trend has peaked.
It's not that they're indifferent to privacy in general. Rather, the system as reached a point where users are satisfied with the amount of control they've been given.
Specifically, they can render their profiles invisible to people they don't know, disengage from people they come to dislike, remove their names from pictures they don't want to be tagged in, and easily limit any personal details (except birthdays) that they don't like sharing.
For an enormous number of people, that's just fine.
I think people online often mistake a vocal minority pushing for privacy settings on this network as a reflection of the wishes of everyone. Truth be told, most people are indifferent to the matter.