Halz, in my experience this is the list of spam-flooded wikis http://wikistats.wmflabs.org/display.php?t=mw&s=ausers_desc: there's no way a wiki with a couple admins and a few hundreds articles can have thousands active users, unless they're all spammers.
Another pattern in spammed wikis is that their dumps compress very well with 7z, e.g. one talk page here compressed about 5000 times: https://archive.org/details/wiki-wikicafe.metacafe.com_en
I agree that knowing what's happening out there is the first step, so something useful to do is compiling a list of wikis to have more examples like these: https://code.google.com/p/wikiteam/issues/detail?id=59 Of the 20k wikis in Pavlo's list of 2009, 75 % are dead now. Spam was probably a component of their death. Actually, spam is probably the first reason people don't create or keep MediaWiki sites.
Nemo