Academia.edu is a social network for researchers, scholars and academics to make their publications available to the general public for free (as a lot of research is published in journal articles or books and the average person would have to subscribe to the journal or purchase the book to get access to that research).  It is one of several research-focused social networks.
One of the things these networks do is share analytical data with the researchers that use them.  Below is a message received by State of the Nation: K-12 E-Learning in Canada lead researcher, Michael Barbour, that indicates the latest edition of the annual report was the most accessed piece of research on his network over the past five weeks.