[Matth]

Precisely - I'd say it's crazy that anyone can edit without joining, when most forums have been forced to limit guest postion to at most a tiny "can't login" corner, moderated with an iron boot.

Though maybe not so crazy, since that means the regulars will have much less trust of ip-address tagged, non-member changes, wheras if every ******* vandal was forced to log in, they would be harder to spot.

The main problems are:
1. Vandalism - adding junk, deleting entire pages or sections.
1a. Incompetence vandalism - saving test junk instead of previewing.
2. Link spam
3. Well meaning, but wrong - adding information that requires a few tweaks is forgivable, messing up previously correct information is not.

The "good people" are the content creators and the helpful wikifiers - you do sometimes find a near symbiotic pair, where the raw input from one gets a dust-over by the other, though it helps if the content creator gets better at wiki wrangling, though if you know that "X" always makes good and sensible edits, then you don't feel the need to crosscheck.

The saddest thing is when you get two people in something that falls one step short of a full scale edit war.

There is also a different dynamic in articles that are already way down the multi-edit, multi-contributor line, and those which are being maintained by one person - NOT really ideal for a wiki. In fact, if you are the only contributor on a topic, wiki is far from ideal.