Social networking sites do uphold an individuals privacy. The sites are not providing our information to anyone we do not allow them to. These sites allow the user to set their own privacy settings. If too much information is given, it is the users own fault, not the site. There are times when a hacker may steal your information but this is not the fault of the site. It is no different than a thief stealing your credit card information. This is the way of the world.
I believe that each individual site tries to the best of its abilities to keep information secure and to keep everyone's privacy, but if it is out there on the internet then there are ways for people to get around and beat the system. Social networking has become so popular that even people that do not have an account with a certain website are still being talked about and photos being shared.