I see a lot of good points being made here, and I frankly don't know what to think about some of the issues raised. But I'd like to offer this perspective.
On wasting time on recalcitrants: I (obviously) totally sympathize with those who say they don't want to waste their time dealing with recalcitrant users.
Wikipedia contributors can be difficult in a variety of ways. Not all of them require banning, and the most common types can't:
* cussedness. I plead guilty, as must nearly everyone at some time or other. People can be rude, dogmatic, uncooperative, etc., on talk pages. This isn't a reason for banning, though--at least, we haven't yet met someone who is so completely rude and antisocial that *that alone* suffices for us to ban 'em. I doubt we ever will...
* vandalism (writing pointless profanity, deleting articles, and other such activity). We have been banning people for vandalism since the beginning, and this is a good thing. In particular, the fact that there is no precising definition of "vandalism" that eliminates all borderline cases is *not* a reason to stop doing it.
* ignoring rules to consider (e.g., titling articles with all caps, writing small amounts of bias, using first person, and infractions of that moderate level of seriousness). We have never banned people for these things, and we never should. As far as I know, no one is suggesting that we should, and that is one thing I'm happy about. :-)
* brazen bias. I think this deserves a separate category: people who repeatedly write really badly biased stuff, even after being told repeatedly that there's a strictly-enforced policy against it. This was Helga's problem; to a lesser extent it has been a chronic problem with some other people. I reluctantly have to agree with a slight change of policy on this point: people who leave no doubt, over a number of days or weeks (not hours), that they simply don't care about the nonbias policy, who keep shovelling screeds into Wikipedia and editing articles *only* to represent their own points of view, should be banned. But this should only be in really egregious cases. Very many people, including people who have been posting on the list lately ;-), write subtly or slightly biased stuff all the time, apparently daring other people to catch their subtle bias. I don't think we should ban people for that, we should just thunk 'em on the head (virtually, of course).
* kookiness. Yep, I think kookiness should be and arguably has been a reason for banning people. If they just won't go away, and they continue to shovel their kookiness into Wikipedia, we should ban them. This was an ancillary but important reason for banning both 24 and Helga, both of whom wrote all sorts of kooky stuff. We're still undoing the damage that 24 did, in fact. The defining characteristic of the kook is (1) saying stuff that's totally false or totally biased, while (2) not knowing, or admitting, that it's totally false or totally biased, and (3) passing their stuff off as legitimate knowledge developed the way other scientific and academic knowledge is developed (when it ain't).
* other kinds of difficulty. People will invent all sorts of ways of being difficult. E.g., not that anyone has done this yet, but if someone were to write perfectly usable but atrociously spelled entries over and over again, I can imagine that that would be a source of much frustration for those who would have to follow the person around correcting the spelling. While people can be difficult in many ways, I doubt there are many more grounds for banning.
* uncooperativeness, i.e., claiming ownership of articles. Now, this is a new category among the alleged "grounds for banning"--and we ought absolutely to demand that we get clear about this before we move forward with any such ban. Being an egotistical jerk is not by itself grounds for banning. Being insolent and insulting is not by itself grounds for banning. Those are both ways of being "uncooperative," but people shouldn't be banned for those things. On the other hand, basically claiming an article for yourself, constantly reverting other people's edits for no good reason, etc., can sometimes (*modulo* the usual concerns about clemency, clear evidence, a demonstrated pattern, and egregious offenses) be grounds for banning, I think.
But this is hard to interpret. I think DW came close to bannability on this grounds. On the other hand, I can easily imagine someone who is a bona fide expert on some topic about which there are some things that nearly all experts would want to say--and *not* say. I can imagine that various people might try to edit the article written by the expert, and the expert might (reluctantly) wind up reverting all the changes, because all the other editors, not being experts, simply were mistaken. This is not very likely, not very common, but I think something like this does happen. Here's where it's unfortunate that we do not have more participation of more educated people, so that we can have several experts acting as checks and balances on each other. But anyway, the point is that the expert who is defending an article against bad edits might appear to want to "own" the article, and thus to be highly uncooperative. I don't think that experts should have to "cooperate" with people who don't know what they're talking about. Just because Wikipedia is open, that doesn't mean that nonexperts shouldn't defer to experts on matters of fact. Matters of bias are another can of worms--sometimes, an expert will give a partisan presentation of an issue, and then defend it because he's the expert, when other nonexperts can spot the bias. In such cases, I think we should remove the bias but defer to the expert on everything else.
====
This is a bit off the topic, but it came up and I can't let it pass. KQ said recently that Cunctator is the project's *conscience*. Perhaps KQ was just trying to be nice, but I think that is actually unfair to the rest of us, who like to think we have a principled approach to the project as well. It also accords Cunc respect as somehow *the* representative of a *particularly* moral point of view, to whom the rest of us ought to pay special heed--I disagree with that and I enjoin you not to accord *any* one person such special respect. (I'm not sure KQ meant to imply all this by "conscience of the project," and I also doubt, in his reasonableness and modesty, that Cunc would reject the description when cashed out as I have done, but I just want this to be clear.)
--Larry