Last week's news about Howard Schultz's return to the helm of Starbucks as CEO got me thinking about second acts. They're fairly common for CEOs. A year ago, Michael Dell was called back to the executive suite to revitalize the computer maker's growth. And Charles Schwab was reinstalled as CEO in July 2004, after having stepped down from that same role just 14 months earlier, in May 2003. Second acts don't seem to be as common for CIOs\u2014or any business executive other than CEOs for that matter. Paul Groce, the partner who leads executive search firm CTPartners' CIO practice, and his colleague Dan Kaplan, put their heads together and came up with the names of just two CIOs who've had second acts: Brian Light at Staples and Preston Bradford at Sapient. Groce says retired CEOs get called back because of their exposure and accountability to shareholders. It's much less common for other C-level executives\u2014whether CIO, CFO or COO\u2014to be brought back because shareholders don't associate them with corporate success, he adds."If the CEO leaves and the company's stock suffers, the shareholders view that person as the savior who needs to return," says Groce. "Who has driven the return of the CEO? It's the board and the shareholders." Groce cited several other reasons why CIOs are much less likely to entertain second acts than CEOs:CIOs are literally out of touch with the business. A CIO who moves to a new company no longer has his finger on the pulse of his old employer. By contrast, a CEO who steps down from his post often remains on board as the company's chairman and thus maintains his association with the business and its challenges, says Groce. A CIO who's left the company does not have the same knowledge of the company that the CEO-turned-chairman has and therefore does not have the same ideas and ability to impact the company as the CEO.CIOs are often responsible for their own succession planning, but CEOs are not. Groce says boards of directors often view selecting the next CEO as their responsibility. So if a new CEO doesn't work out, the board may beg the chairman to return to the CEO role.If a departing CIO appoints a successor who fails to measure up, that CIO will be viewed as having failed in his succession planning duties, and thus the management team with which he worked may not be inclined to invite him back to the table, says Groce.Moving back into the CIO role can feel like a demotion. A CIO who moves into a new role with his company may not want to go back to the CIO role, even if the management team pleads with him to do so and considers him to be a knight in shining armor. I thought of two circumstances under which a CIO might be called back, however implausible:A retired CEO is asked to lead his company again, and he decides to replace the existing management team with his old management team. If a company moved its CIO into a different position, and the person who succeeded the CIO proved to be an ineffective IT leader, the company might ask the CIO to return to his prior role, even if it's just temporarily.Can you think of other CIOs who've left their companies or moved into different positions within their companies only to later be called back to their old role? Who are they? What were the circumstances surrounding their second act? Under what business conditions do you think a CIO could be asked back?