I've been doing a comparison of query results using Webmaster Tools, and I've found many, many phrases for which I ranked #1 to #5 on Monday, and now rank anywhere from #30 to #150. What changed with the quality of those pages?
I also did a search today for one of my phrases, and found the title of the first search result to be rather amusing. It was "404. Page not found". I kid you not.
Maybe they got Sergey's mom to sew the Google uniforms, and everything is being run from Larry Page's family's barn.