San Diego-based WebSideStory has lost its CFO to Cost Plus, the firm reported yesterday. Tom Willardson, the company's CFO, will leave WebSideStory in January to become EVP and CFO at retailer Cost Plus. Willardson is currently on the board of the Cost Plus. WebSideStory said that it will initiate a search for a new CFO immediately, with CEO and Chair Jeff Lunsford covering the duties of the CFO until a replacement is found. WebSideStory is a provider of web analytics, content management systems, and other web applications.