This looks like the next wave of spambotage, doesn't it? Seems that a vast number of wikis have been trashed and replaced with porn links, and all the damage has been done from a Russian IP address. I can't really imagine anyone being sad enough to sit down and go through thousands of wikis this way, so it must be a bot.
How vexatious. I wonder how you could stop this kind of thing? Short of declaring open season on spammers, that is.