Welcome to WebmasterWorld Guest from 18.104.22.168
I'm hearing some reports of site-wide ranking demotions over the weekend that have a similar pattern to what we saw with PandaA keyword that I had put a little work in chasing was hit last Friday, the top sites that have replaced page one are the wordpress type sites that were dropped around May / June, pretty poor content sites.
AFAIK nothing too crazy right now. It's hard to predict which of 500+ algo updates/year will attract attention though.
Google has also dispatched principal engineer Matt Cutts, a plain-spoken Kentuckian with a knack for demystifying the company's search algorithms, to rebut arguments that Google favors its own products in search results over those of its competitors.
I am not sure if it was Panda or a prelude to something about to happen.