Whilst this technique may be mostly effective for a single person reading an online community through a client application - because they simply do not see interactions with the UnwelcomeVisitor involved - it is merely a method of treating the symptom, noise, rather than the deeper cause, which may be a PersonalityConflict or one of a multitude of other reasons. Often the KillFile fails. Conversations will continue between the censored and others in the community. What you see looks much like a telephone conversation as heard from only one end. This can become very annoying as you know there is something you are missing. If the intended target talks about you, you will find it difficult to keep the person ignored. Often you will see people emplore others to KillFile the person rather than engage them. This frequently degrades into falacious and naive arguments about FreeSpeech and the need to engage people in a conflict rather than ignore them. The SignalToNoiseRatio in the community may drop as arguments flood the community about whether or not to censor the malcontent have to be made on AnIndividual to individual basis. Further, individual choices to filter the PublicCommons? disrupt or even destroy the commons as the PublicArt at the centre of the community; it no longer remains something in common.
Worse, the malcontent may attract new blood into the conflict by soliciting newcomers just in the VisitorRole or the GuestRole. A coy malcontent will be very nice to a newcomer who remains unaware of the conflict. The newcomer will see the veterans fighting with what they perceive as a nice person, and they will conclude TheCollective is deranged. Even if they don't, most newcomers will AvoidConflict rather than jump into the middle of one. This is another form of the HighLowPump?, and particularly vicious since it cuts the OnlineCommunity off from its source of new members.
Rather, a community is responsible for the security of its membership. A KillFile puts the onus onto TheIndividual rather than community. Communities suffer if they cannot guarantee a safe environment, and you will see valued CommunityMembers exercise their RightToLeave rather than use a KillFile. They may not know of KillFiles, find them too hard to use, or get tired of having to continously mount an ActiveDefense? and an active campaign against the malcontent.
When an entire community decides to KillFile someone, this makes the target a CommunityExile - an extreme form of DissuadeInteraction. This can perhaps be considered a form of CollaborativeFiltering. If that is the case, it is probably better to look into HardBanishment.
See also On building killfiles into your communities, by TomCoates?  and CommunityWiki:IgnorePeople.