Here's a post concerned that Facebook is rooning teh internets by destroying our authenticiteh. It seems a bit OOT to me, but it's very much the opposite viewpoint to Farhad Manjoo's. [Edit, I should note that the author says that anonymity is not his main/real point, though his real point does seem to be about the ability to create multiple online identities for different contexts.]
I expect that we'll continue to see some sites require people to use their Facebook identities, but others would be destroyed if they tried such a thing. It'll find a level.
Anyway, I had to laugh at this:
Face it, authenticity goes way down when people know their 700 friends, grandma, and 5 ex-girlfriends are tuning in each time they post something on the web.
In my case, it's a smaller number of ex-girlfriends on Facebook, and certainly not grandma ... but over 1800 friends.