Looks like recent scandals related to the Spanish report "Operation Puerto" have now knocked out Jan Ullrich, Ivan Basso, Francisco Mancebo and more...
Operation Puerto: The list (Eurosport)
UCI add names to official list (Eurosport)
Spirit of '98? Surely not (Eurosport)
Basso and Mancebo out of Tour (ProCycling)
Ullrich out of the Tour de France (ProCycling)
More riders suspended: Basso and Mancebo out (Cycling News)
Operation Puerto: Yet Another Doping Scandal (Centripedal Blog)
Black Friday: Basso, Mancebo, Ullrich all withdraw from Tour (TDFBlog)
Doping Scandals Throw Tour de France Into Chaos (NY Times)
Updated Rider Listing (Tour de France site)
One final quote from the Ullrich story to give you an idea how serious this is:
"The only thing I can tell you is that the information is clear enough and didn't leave any doubt."
— T-Mobile PR Luuc Eisenga
I guess this year will be quite interesting indeed.