One school of thought is Herbalife could simply have experienced a "dead cat bounce" and is on its way back lower. The other thought is that investors are brushing off Ackman's claims -- maybe he is becoming a fade.
Ackman also recently became a major shareholder in JC Penny (JCP - Get Report). Like many, when I read that I was enthusiastic to see positive changes in the company. Unfortunately for JCP investors, the stock closed much lower at the end of 2012 than at the end of 2011.
Considering the size of Ackman's position, it's fair to assume shares will fall further if Ackman liquidates his position anytime soon.
By the same note, it's fair to assume that shares in Herbalife will increase if Ackman has covered his position in whole or in part.