Social networks have the mass of merits. They allow people to be in touch even if they live in the different cities and even the countries. At the same time it is possible to communicate fully with interlocutors, to share with them news from the life, to show own photos, to give references to the interesting websites. Now many look for work with their help, are engaged in self-education, and the number of those who have found the second half thanks to these services, constantly grows. And, nevertheless, social networks have not only pluses, but also minuses, some dangers about which it is necessary to know are behind appeal of social networks. The most important lack of social networks – the publication in free access of personal information on the person. Most networks collect much more data, than actually it is required for registration.