I personnaly think that virtual social networks may be dangerous because of the power given to the members. Anonymity strengthens negatively the feeling of impunity behind a screen. As a consequence, some people feel free to express themselves in a way they would never dare to use otherwise. As a matter of fact, a face-to-face relation obeys social rules which disappear in the virtual world. This can lead to dramatic situations of harassment difficult to control. Even if the social networks on the Internet can do a service, I think that the traditional networks are more reassuring. However, new Professional links provided by specific networks like Viadeo or Linkedlin may be much more efficient than a usual network. But those kind of links between people are very much goal oriented and leave no room to power abuses.
Many are going to say that it comes with the advancement of internet and technology and all, which is true, because it's a pretty open thing. Then again every great invention can be deemed as a dual-edged sword, and we have to learn to put up some regulations of sorts in order to ensure some peace and 'security'. But social networks today are revolutionary. It's being used to arrest criminals and was used to organise the Arab Spring, and so much more!
It has provided us with more power to control certain things. Some have let it consume their lives while others use it limitedly. Whether or not if it is too much power depends on how the person uses it and if they can easily unplug from it all.
For instance, it makes the serial killers job a lot easier to choose his vulnerable victims,
It gives the old people power to deceive little children,
The enemy power to retrieve restricted information of his opponent,
It gives society power to overcome and corrupt innocent minds of developing teenagers.
Social media right now performs checks and balances on the current 24-news media bullshit cycle which is no longer journalism. This is a good and necessary function.
And, at the end of the day, it isn't the social networks that give people too much power. It is people putting too much stock in certain people, putting them up on pedestals.