Maybe I have missed the point. As Murph of Common Monkeyflower suggests:
You wrote in your blog the other day here that you'd like Wikipedia to have bylines so that you could account for the author's bias. It seems to me that you're missing part of the point of the wiki format...Thank you. Interesting perspective.
If you (or any given person) considers an entry to be biased, they have but to rewrite it, sans bias. Of course, the first person might think the rewrite is biased, and they'll re-rewrite it, but eventually you'll stabilize on something which everybody can agree is good/fair enough to stop revising.
More useful than credits, then, would probably be just the integer number of people who have edited the page. Given a name--or six names--you'd have to go looking at their other stuff and trying to guess their biases, but given the information "6 authors" vs. "1 author", you could probably bet that the multi-author post had fewer shocking errors in it.
Beyond 'bias' Wikipedia is limiting its credibility by the anonymity of its authors. No?
Regarding bias/credibility, it is obviously true that you can trust information from a known source more easily than info from an unknown source. Forcing all contributions to be signed and guaranteeing that all signatures be genuine, though, would bog down the wiki with administrative overhead. The strength of the wiki model that the wikipedia is trying to tap into is that anybody and everybody can contribute, fix mistakes, and root out spin or bias. How well this works in practice, I can't say.Hmmm...Let me think about this.
Digging around a little, it looks like they're not completely anonymous. The page "Wikipedians" (https://www.wikipedia.org/wiki/Wikipedians) claims that there are 750 self-identified contributors, 13000 registered accounts, and lots more edits that come from completely anonymous sources. If you subscribe to the open source idea that more eyes = fewer errors, then the number of people who appear to be working on wikipedia would seem to indicate that the information probably isn't heavily slanted in any direction.
A lot of the identified authors note links to their other webpages, as well as noting which pages they worked on. Pages also have "Page History" links, allowing you to see who (by ip address, if not user name) edited the page when, and to see each version of the page. So it's not completely anonymous (though ip addresses aren't the most informative things in the world).
UPDATE: No there is something about anonymity that bothers me. I like to know who I am talking to or listening to. I've been involved with on-line discussions in which one of the discussants had a nom de web and I thought it slightly strange. What are they trying to hide? What's the big deal? We're talking about urban planning for god's sake, not nuclear weapons. (You see that's the same kind of peer-group pressure which would arise in buying transponder credits etc. etc.)