How?
I went to high school in one city, college in one 1,000 miles away. Have since worked in cities all over the world. I don't know how I would manage to keep even a tenuous grasp on all the connections I have with people in these different places without Facebook. Admittedly, these are not and never will be deep social bonds I am maintaing, but that is hardly the point. There is value in maintaining a large web of shallow social connections. Facebook helps me do this.
Moreover, whether or not Facebook has improved the life of me or anyone I care about is irrelevant to an objective evaluation of the site's value. I could make the same case for anti-malaria drugs.
That is, the connections may be shallow while we're far away, but when locations change again, its nice to be able to re-develop those shallow connections into meaningful ones.
If you think there's no value in maintaining shallow social connections, then I think you too need to put some energy into adding meaning to your social connections.