I seem to occationally get errorsafe popunders + triple pop ups from valueclick lately when using Internet Explorer. I tried Valueclick popup code on a blank page and after a few attempts spanning two days or so I got one so there is definetely one lurking in rotation under some other name
You'd think their quality control people would have some sort of automated check that tests all the adverts regularly from different geolocations, browsers, platforms etc... to catch these sorts of nasty things.
It's good that you can disable ads yourself, though I get the impression they rely on publishers to report campaigns-gone-bad, but given how many campaigns they have, it can take me hours looking through them all.
I really don't understand why it's so hard for ad networks to keep this crap out of rotation.
It's because modern networks accept advertisers with small budgets and allow them to run their campaigns externally so they have full control of the content. I also think networks in general are really poor at validating the authenticity their paying clients these days.