I think that a lot of what ccc is noticing is the natural cultural shift from tech savvy early adopters to main stream users. In the more wild west days things were small and honestly less overt sharing was going on. Even if the web was a central part of your life most of what you were doing was behind closed doors and you were aware of the distinction.

The mainstream audience just doesn't care to understand it as much. They see it as exclusively a gateway to social networks. And social networks encourage you to over share and then make it very hard to reel things back. On most sites I know of you can't have different privacy settings for older posts.

Because social networks make it so easy to over share and so difficult to hide the past, there is this apparent movement to make it socially unacceptable to look back too far in the past. At best I think it'll give users a false sense of security, but Facebook has already proven that once you have critical mass and become the social hub people feel unable to leave, even if they want to.