I didn't change my privacy settings, because I already assume that everything I do on Facebook is essentially public, like any other bulletin board type service.

Also, I only connect to Facebook via Chrome, on my desktop Mac at home, where I use Firefox for all other browsing; on my phone and laptops, I don't use Messenger or connect to Facebook at all. I'm sure they have found sneaky ways of figuring out more about me than I'd prefer, but not so much that additional security precautions seem worthwhile.