Well, I got taken in by the spam job on our Wiki yesterday. 15 or so pages were modified, and I didn't see anything when I eyeballed them - so I left them alone. As it happens, there was a ton of pharmaceutical spam buried in each modified page, using a hidden div. I hadn't noticed, but one my colleagues did and fixed things.

I have a script I use for mass restoration when this sort of thing comes up; I guess I should have used it. One more nasty trick to keep an eye out for...