I spotted this interesting article by Cade Metz on The Register, which highlights the opaqueness of site ranking demotions by Google. More specifically, it makes reference to a technical "indexing glitch" on October 22, which saw many websites' rankings drop for main keywords. The article can be found at: http://www.theregister.co.uk/2010/11/11/google_search_october_demotions/ I hope this is of interest, Marc.
Here is a quote from the article Google competitor and still depending on Google for traffic? Haha...
He should have made his own portal to get the user's attention. Stand out and not go along with Google's moves and algorithms...I cant believe that he even have the guts to make complaints.