I had my wiki locked for anonymous editing to get rid of spammers. Only one or two pages were editable because I wanted people to be able to work on them. I was hoping that spammers would turn down if they can’t find an editable page ad hoc. Not so.
In “return” they did not only spam the open pages – they also replaced and thus deleted the original content (they used to append stuff to existing content). In addition they also started to add new pages below the editable page (which seems to work if the original page is writable).
Luckily I was able to repair the damage, but I wonder how all these Wikis out there surive.