I think you forgot about the 1% or so of useful information from our friends and family, that is the reason for having a facebook account, but the internet is not facebook, most people I know don't use slashdot for example but slashdot does cater to some of my interests. Soylentnews is now overlapping quite nicely with slashdot similar subjects but a lot less spammy trolls. It's probably not going to stay that way.
There are quite a few other sites I use as well such as photography sites , gardening sites and others ebay is useful to me for buying relatively obscure items that are not available locally. there are local market place sites to use as well for example donedeal.ie is good for finding cars in ireland adverts.ie can be a handy place to find items locally.
So honestly facebook is just a feed to me of things i might actually care about and a lot i don't. I don't think i am unusual in using it that way. The instant messaging side of facebook is also handy when there is something i want to talk about with a particular person.
I honestly don't believe facebook has what it thinks it has, because most of the stuff that matters to people is not done on facebook and g+ is a complete failure because it doesn't provide anything that is of any use. one feed of mostly useless crap is enough.