4chan is an example of an "anonymous" system, not a "pseudonymous" one: the difference is whether you have stable identities over time, and therefore can build up reputation (positive or negative) for a particular "pseudo-name".
As long as you have mechanisms, whether social or political, to "default distrust" new users that don't have much "cred" yet (mechanisms like the "green" user rendering that Hacker News uses for this purpose), you are not going to lose the benefits of "anonymous" vs "real names".
In fact, one might even argue that claiming otherwise misses the point of names: even when I am going by just the name "saurik" (seldom, but it happens: like here on this site), I care deeply about what I say as it affects my identity.
As an example near and dear to many people on this site, no one had known who "why the lucky stiff" was (maybe they do now? not keeping up with that much); but, if he had started being an idiot on forums and started "proliferating senseless hacking and child pornography", you can be certain that that would have been quite bad for him.
(In fact, if your real name is not known by anyone, and everyone knows the entity that actually has all of the reputation capital you draw on on a daily basis, then arguably there is no risk in doing something stupid with your real name, and total risk in doing so with your pseudonym.)
I agree with you on two points. Firstly, you are right to make the distinction between anonymous and pseudonymous, they're two different things and you can build a reputation system and healthy community on a pseudonymous system (see HN). However, I think they both exhibit the same underlying problem that comes with lack of accountability. HN has been lucky, because it's for the most part an elite community full of smart people. Digg or reddit have not been so lucky, and the quality of comments there is quite low. HN is the exception, not the rule.
Secondly, I also agree that there's definitely some edge cases where it make sense for people to be anonymous, or pseudonymous. If you need to shield yourself from your employer for legal reasons, I think it makes sense for you to do so. What I'm arguing is that in most cases, though, it's good for the overall community to enforce true names.
I use a pseudonym to shield myself not so much from my current but my next employer. Or landlord. Or girlfriend's family. HN gets what's really weighing on my mind, while Facebook gets heavily censored, cheerfully inoffensive pablum when I bother to participate at all. As I see it,
true names : pseudonyms :: villages : cities
and cities are the wellsprings of progress because people can reinvent themselves and unpopular but good ideas can find support.
There's more to pseudonyms than legal reasons. What I write on the internet stays there, and I expect people to google my real name, but I do not wish to have all of my lives linked together.
For example, if I'd have to use my real name, I would never speculate. With a pseudonym, I feel comfortable making mistakes and tiny contributions. Similarly, if I were in a horde guild, I would not want alliance players to dismiss my civil politics opinions.
As long as you have mechanisms, whether social or political, to "default distrust" new users that don't have much "cred" yet (mechanisms like the "green" user rendering that Hacker News uses for this purpose), you are not going to lose the benefits of "anonymous" vs "real names".
In fact, one might even argue that claiming otherwise misses the point of names: even when I am going by just the name "saurik" (seldom, but it happens: like here on this site), I care deeply about what I say as it affects my identity.
As an example near and dear to many people on this site, no one had known who "why the lucky stiff" was (maybe they do now? not keeping up with that much); but, if he had started being an idiot on forums and started "proliferating senseless hacking and child pornography", you can be certain that that would have been quite bad for him.
(In fact, if your real name is not known by anyone, and everyone knows the entity that actually has all of the reputation capital you draw on on a daily basis, then arguably there is no risk in doing something stupid with your real name, and total risk in doing so with your pseudonym.)