Hi, i am creating an e-learning website that allows people to buy Education Courses for other people (college friends etc...). Receivers of these Courses have to sign into the website to complete various tutorials each day. A live activity feed is on the home page of the site and it shows the different activities of each of the users...

I have seen the "Sign In With Twitter" and "Sign In With Facebook" options on many sites, what are the real advantages of adding this feature to your site. I am trying to weigh up whether it is worth my time adding this feature to my site, thanks in advance for your help...