If your users post copyrighted material, e.g., then you'll be offered safe harbor only if you enforce registration via the national ID. Same deal for people posting "naughty" content -- which is more insidious than it sounds, because of the overlap between (a) sexual content and privacy concerns in discussions about, e.g., STDs; or (b) in the wake of wikileaks, being hassled about publication of, or support for those publishing, "leaked" data be it from government or from industry.

It's necessary that we provide a way for people to maintain anonymity, but the government wants to offer enough carrots to divert our horse from that path.