No Web 2.0 privacy
Web 2.0 is just not there yet: There's robot.txt on traditional web sites to gently ask search engines not to index the pages where it resides, but there is no equivalent standard for social web sites, like a checkbox in your user profile to request not to be indexed by search engines.
Of course, truant bots can always bypass this request that relies only on "good behavior", but web 1.0 and 2.0 might prevent that with proper file system or database authorization management.
The current situation is real bad, many social sites do not even offer a basic feature to delete all traces of your account, and each of them manages privacy differently and in their own way just like they want, not like the user wants.
With all employers now looking up your name on the Internet for job applications, it seems like a basic privacy protection measure for kids and teens to systematically use a pseudo online identity, I wouldn't even want to change it to a real ID when reaching adulthood, the same problems apply. Just saying...