Many social sites claim in their usage terms the right to use any of the information you provide in any way they choose. Visit the Facebook Terms of Service page for an example.
If they own your content and profile and decide to reuse or resell your information (for example to sell your personal information to an advertiser or use your granddaughter’s picture for advertising), there isn’t much you can do about it.
In addition, even if you select the Private setting on a social-networking site or discussion forum, your profile settings are typically public. When you sign up for a service and provide the required information, selecting the private mode may not prevent your photo, name, URL, city, state and date you last logged in from showing. Check your public profile after you sign up to see what’s exposed. If you’re not comfortable with the exposure, remove some information or close your account. This information can be used to help ID thieves, cyberbullies, scammers who pretend to share your interests and other criminals.