I found some of my key images there through Media Bakery with attribution to my name. I presume it's one of those partner arrangements with IS, SS or DT.
I did a couple of searches where I have an 'istockwhack' and didn't find my images, so either they're not (yet?) iStock affiliates or not all images are indexed. Not at all impressed with their search, which was throwing up all sorts of irrelevancies.
Did find out about the existence of loads of agencies I'd never heard of, though.