for a satisfying communication with a system like wiki and her sisters (well, actually for all kinds of open dialogues) a few things are definitely indispensable: discussion culture, self-criticism, pluckiness and honesty are among them. but probably most important is to pit oneself against the forces of wiki's nature er, i mean: to put up with the consequences of free editing.
eradicative deletion is bloody easy (and bloody, bloody stupid, no doubt) with those tools: everybody can do it anonymously and someone always will (think of murphy!) whether it might be to adjust history or simply for the means of destruction.
but hey! this is the most interesting part of the wiki concept! sure it would be possible to reduce such risks e.g. by obligatory membership or by implementing a cvs behind it (a weird idea anyway?). but if the tension is taken away self-organization will be irrelevant. why using wiki then at all? just be aware of it and of your wildest expectations coming true you won't fail.
see, even the big boys have been struck by tricky wikiness.
a description of document mode which can be useful to summarize a thread (instead deleting it) avoiding it to e.g. completely turn into a meaningless flame-war. become a wiki master, boy!