I found Facebook useful back when I was single - less creepy than real dating sites, and much better coverage of people from my circles. But even that utility is diminishing, as people appear to do less there.

Of course, I know many people who practically live on Facebook, but I suppose that is mainly due to boring desk jobs instead of actual gossip addiction.

If Facebook starts winding down, it will be interesting to see how all those millions of sites relying on FB for their social features and authentication cope.