Michael M. Santiago/Getty Images Shares of online ticket seller StubHub dipped in their debut on Wednesday. The company's IPO had been widely anticipated by investors. The stock failed to generate the momentum that carried others to big post-IPO gains recently. The move: StubHub Holdings stumbled out of the gate on Wednesay, dropping as much as 6% in its stock-market debut. The newly minted STUB ticker initially surged 7%, passing $25 per share before quickly reversing course and falling to$22 aft ...