For the past three days we have noticed dramatic movement of some websites, including sites disappearing from the index. They are not necessarily adult. I think Google is going after the various scraping mechanisms with a vengeance. This happened previously only about 3 weeks ago, in late August, which seemed to set the stage for the release of Instant only a little over a week ago. I think the algorithm for Instant's results was in place on Sept. 1st, but it took almost two weeks to get the functionality live. We are West Coast in San Jose, and the OP's mentioned site is gone from our data center as he and others have said.
The interesting thing about what happened in late August was that some sites that disappeared for several days ultimately came back to their original positions. The sites that came back tended to be the ones that created their own carefully constructed link pyramids, as opposed to gratuitous scraping. The fact the the pyramid sites went away for siesta for a few days still troubles me, because it shows that Google can at least recognize some fairly well constructed link pyramids well enough to make them candidates for deindexing, only to put them back later after, I suppose, concluding that they are OK. Makes me think that some of our pyramids may be in danger as this algorithm progresses.
One other thing we have noticed is some extremely heavy network traffic going through some of the co-location facilities here in the San Francisco Bay area, and in Irvine in Southern California. We don't know what it is, but it is clogging up the internet for the last three days, causing slow net response times, and even some net bandwidth alarms. Everyone assumes it is a virus, but I think that index propagation at Google can cause this, especially when we are all using essentially the same backbone here. Not much we can do about it other than move out of the area with our data, but it happens all too regularly since the beginning of 2010. We never saw this before this year. It really makes us wonder what is going on at the big G.
Here on our block in lovely Black Hat Estates, everyone is either a Google millionaire, a black hatter, or a corporate sexual harassment lawyer. Some have intermarried. Needless to say, this makes conversation with the neighbors difficult, not to mention pillow talk. But I may be able to eventually figure out what is going on and I will let you know.