Here´s how it is folks, sorry to be blunt:
Doping control (WADA and USADA, and other domestic agencies) basically doubled their budgets as it was an olympic year, and were hounding athletes for their whereabouts, doing surprise tests, and in general making it difficult for athletes to get away with anything. That being said, guys like Wariner and Tyler Christopher, both of whom underperformed last season, weren´t able to get away with doing the crank all year because of it. Furthermore, information was leaked that doping officials were wise to the new version of EPO being widely used that previously had no test.
In summary, Wariner will be able to dope it up once again next season (a bit more anyways) and will therefore be faster. Its very simple.