... Are you really asking what friends are for? It's just a way of showing your affiliation to different members of the site. Saying, "this person and I are cool with each other and are friends." What else could it possibly be?
^ Yup Yup. I've made two friends on the site since joining and I recognize them right away. If you've read someone's writing in the Workshop and like their style, or someone has given you valuable input you respect, you could friend them and keep in touch in order to ask for support and read whenever they make a Blog Entry. I'm new here, but that's what I think ^^
Some profile security settings put friends in a higher access category, or at leas allow the member to grant more access to friends. When the site software is upgraded, there will probably be more settings that can take friend status into account. Personally, if I can't handle the world seeing it, it doesn't go in to my profile for anyone. That's why you won't find an email address of a messenger ID in my profile. Doing so invites spam and other forms of harassment.