More than half of chief information officers surveyed by Robert Half Technology reported that their companies do not allow employees to visit social networking sites for any reason while at work. The poll was conducted by telephone and was based on interviews with more than 1,400 CIOs in companies in the United States that employ 100 or more workers each. Fifty-four percent said their companies have a ban on use of such sites during company hours. Only 10 percent allowed unlimited use of social networking sites.