Social networking sites are disasters. Social networking sites are nothing more than tools for narcissists. Social networking sites are increasing in popularity but are really destroying natural and healthy interpersonal relationships and foster ignorance of the human condition. Take this example, recently two girls fell into a sewer and though they had their cells phones with them, didn't have the common sense to call for help, instead they just updated their Facebook pages until someone figured out they were in trouble and called help for them.
No, because we never needed them before, so why now? We have functioned as a society for hundreds of years with nothing more to communicate with others but a pencil and paper. Is it easier and more convenient? Yes. Beneficial? Not really. Not when you take into consideration that people could be doing so many more things in their spare time, instead of looking at a computer screen, watching what other people are doing. Which is also staring at a computer screen.