Updated from 1:10 p.m. EDTOpposition is mounting to eBay's ( EBAY) plan to expand its pool of stock options, with the nation's largest public pension fund deciding to vote against the proposal. Calling it "excessive," the California Public Employees' Retirement System, or Calpers, said it will vote its shares against the plan. Calpers owns 213,000 shares in eBay, worth about $21.6 million in recent trading. eBay did not return calls seeking comment. Not only do options dilute shareholder value, but corporate governance critics have linked them to the scandals at Enron and WorldCom, charging that their use tends to encourage short-term -- and sometimes illegal -- actions to boost stock prices. While not among the very largest institutional holders of eBay's stock, Calpers, with its $138 billion investment portfolio, is among the most influential. And it is taking a reformist bent in some of its votes.