I think Facebook is beginning to have systemic user privacy/comfort issues resulting from their persistence in oversaturating their social graph. yan is right in that only a tiny minority of their userbase (such as us) really cares about this right now, but I think that in this case our concerns are leading indicators for those of the rest of the Internet-using population.

I don't think that any site that tries to combine the entirety of the social graph with contextually agnostic personal content will ultimately be successful - in other words, no one wants a site where everyone they've ever met can see what they're doing all over the Internet, and this is what Facebook seems intent on creating. It's more than just a pure privacy concern (where privacy means restricted access to personal information) - there's also filtering issues, with my 'friends' being exposed to/spammed by content I create that simply isn't meant for them.

For what it's worth, I'm also actively working on an alternative to Facebook, which will be a tool for users to partition their online social network to match their real-world social contexts, and then use those partitions to manage their 'friends' lists on the myriad other sites where people already share content (Flickr, Foursquare, Vimeo, Twitter, and so on).