Some social sites allow us to suggest friends to our new friends. Really this feature is a good option to increase our friend circle. As well as we introduce some of our good friends to our new friends and extend the friends circle. I think this option is available for the newbies who don't have more friends.
If you are joining with a social site as a newbie with your friend's link, you don't have more friends in that site. Your friend who introduced you may suggest his/her friends to you to extend your friends circle. By this way, we can come to know about new friends as well as getting common friends. We have more fun and enjoyment while interacting with more friends and extending our friends circle.
We can suggest some of our good friends to our new friends and make a lot of common friends in social site, which help us to form friend's group. We can suggest our online/offline friends to our friends. Recently one of my real life friend joined with a social site with me and i suggested some of my good friends to him as well as send a message to my friends about him. Now he have lot of good friends with my suggestion and increased his friends circle.
Social sites are good to find new friends as well as share our common friends and have fun with them. Surely we must suggest some of our good friends to our new friends to help them to enjoy a lot in that site.