Unlike relationships in the RealWorld where you can presumably make a direct impact on an individual (you can punch them), online you can only make indirect impact on individuals. You can only hamper them or restrict them, but they can surely come back to annoy you or attack you in other ways if suitably provoked. For instance, if you have a login system, deleting their account won't stop them from creating a new account, which is why LoginsAreEvil.
Worse, punishing people with emotional ties to the community will only anger them, which has the unintended effect of strengthening the emotional attachment to the community, although dramatically changing its character for the worse. You stand a very high probability of facing repercussions from a angry former community member. And let's not forget the most fearsome attackers are those from the innermost circle of the community. Of course, even people new to the community, such as l33t hax0rs who are subsequently CommunityExiled will only take that as a cue to attack harder. LimitTemptation, after all.
While we do not fear attackers in every corner, as we DefendAgainstParanoia, it's not paranoid to avoid losing friends. It's hard enough to ForgiveAndForget a mistake without multiplying the damage with punishment. People, even enemies, will actually respect you more if you can find it in your heart to forgive people after the initial confrontation.
In any case, it's vital to avoid creating an atmosphere of anti-community. While your target may be one disruptive thirteen year old, you may inadvertently discourage a valuable contributor from participating in such a negative environment. Furthermore, if you start eliminating individuals ability to gain reputation, such as SlashDot's infamous bitchslap for KarmaWhores, you will remove any motivation for them to behave. This will only make them more disruptive.
I think there is a conflation between geek culture and mainstream Internet culture. Geeks follow a highly competitive meritocracy, with a highly evaluative human relationships. That is, they categorize and judge people (too) rapidly, which is after all what they do all day when programming: break the problem into cases and then act upon them. Those techniques run opposite best practice in management theory and justice theory.
The general philosophy of the Anglo-Saxon justice system was to act on behaviours not intentions, and thus one cannot label someone as you don't really understand their intent. One just says vandalism is wrong, so if you do it, we will punish you. However, Anglo-Saxon cultures have moved progressively towards a more psychological approach, seeded by the need to establish motive. We discovered some people have no motive, so they entered pleas of insanity. Now we have moved into intent-based (thought?) crimes like hate crimes and terrorism, although these seem to be shoe-horned into the previous framework. Consider the result of this outcome is that the crime is to hate us, so if you hate us, we will punish you--but does that actually result in less hate or more hate? Other justice systems around the world are more participatory, concillitory, and communal.
Moreover, these personal systems may serve better in small communities where emotional connections between all participants are strong rather than in large societies where it is possible to "anonymize" and abstract defendent, prosecutor, judge, and jury as one can select each independently from each other. Note however the injustice of celebrity trials where it is impossible to find an impartial jury. That is, in small communities or with famous individuals, there is reputation, which thwarts the process. While the Internet is seemingly anonymous as it is already over 100 million people spread throughout the globe and growing, within certain subsets it is tightly connected, such as within the Greater Wiki Community as well as the Greater Wikipedia Community. It is impossible to find fully impartial judges in these communities. Hence, a behaviour-oriented approach will not be successful. You can only use such an approach on someone yet to integrate into the community, such as drive-by vandals. -- SunirShah
This phenomenon isn't really about reputation, it's about punishment. An author can form emotional ties with the community, even though they have no reputation in the community, when they PostAnonymously. Reputation is just a reinforcement of the punishment. -- JohannesGijsbers