As a student, there was a need to make a website with a small social functionality: a list of people who studied or are studying in my faculty. You can make a registration form for graduates, but this information is in abundance in our social networks: Classmates, Vkontakte, My Circle, etc.
There is it, but you will not pull it out automatically - none of these projects have an API for this (Odnoklassniki and Vkontakte have no API, and most likely will not).
I could display a simple list with photos on the site, and the links would lead to a social network. I would get the necessary content, and the network - the visitors and potential users. Instead, social networks eagerly collect information about users, and do not want to share it. ')
This kills any idea of Mashup in runet, the creators of these networks need to look in the direction of Facebook, which with integrated applications was able to gain great popularity.