For me, it has some limited use. It helps me keep informed about friends who have moved away, for example.
Besides that, its benefit is very limited. I've deleted so-caled "friends" (or hid them from my News Feed) because they post updates on insignificant things and do nothing but clutter my page with nonsense.
I think Facebook can potentially damage relationships. For example, I've made friend requests that have been ignored by people with whom I work or whom I know personally. While it's not a huge deal, in the back of my mind I do wonder why I was rejected.
Also, I've deleted people, as I mentioned. How do they feel about being deleted? Could they resent me for ultimately rejecting them?
Some people get very offended when relationship status is changed. It's fueled attacks against an ex who try to move on. There's a lot of stalking by exes on Facebook.
It does make one wonder if the negatives don't outweigh the positives.