Underlying driver here is that users are migrating en masse to Facebook now for their professional updates and post streams. Twitter is most impacted, but LinkedIn too. That's why TWTR selling, LNKD sold. The market for users attention, not just the market for their stocks is moving against them. FB is like the wandering Jupiter of our early solar system- the 'grand tack' is sweeping up the smaller bodies in the solar system. Good to be Jupiter..
I just use (or avoid using) facebook for totally different reasons than I use twitter.
On twitter I mostly communicate with people I've never met and have little association with apart from shared interests. It's a great way of meeting new people.
Facebook is for communicating with people I already know, many of who are actively searching for alternatives but because "everybody uses it" are locked in.
Interestingly, I've avoided using Facebook as much as possible. I keep the profile alive because my siblings expect me to have one and tag me in stupid things I don't allow to actually show up on my wall. I actually log in maybe once every six months because there's nothing to see there, just re-shares and tired memes. Twitter on the other hand I use pretty much daily.
