Twitter Inc.'s directors and top executives are holding on to shares that they own and are committed to the business, Chief Executive Officer Dick Costolo said at the microblogging service's first shareholder meeting. The company faced questions in the 37-minute meeting at the Hilton in San Francisco yesterday about restrictions on speech overseas, philanthropy and recent share performance. Twitter's stock price has declined by 50 percent so far this year, fueled in part by a broader selloff in technology shares. After the lockup period for insider shareholders expired on May 5, the stock slumped 18 percent.