Reacting to an online swell of suspicion about changes to Facebook’s terms of service, the company’s chief executive moved to reassure users on Monday that the users, not the Web site, “own and control their information.”

The online exchanges reflected the uneasy and evolving balance between sharing information and retaining control over that information on the Internet. The subject arose when a consumer advocate’s blog shined an unflattering light onto the pages of legal language that many users accept without reading when they use a Web site.

The pages, called terms of service, generally outline appropriate conduct and grant a license to companies to store users’ data. Unknown to many users, the terms frequently give broad power to Web site operators.

This month, when Facebook updated its terms, it deleted a provision that said users could remove their content at any time, at which time the license would expire. Further, it added new language that said Facebook would retain users’ content and licenses after an account was terminated.